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Bureau of Mines Information Circular/1985 




Cabs and Canopies for Underground 
Coal Mining Equipment 

Proceedings: Bureau of Mines Technology Transfer 
Symposium, Charleston, WV, June 22, 1983 



Compiled by William W. Aljoe 




UNITED STATES DEPARTMENT OF THE INTERIOR 



DD 

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75 

'l^/NES 75TH AV!k^ 



Information Circular 8996 , , \ ^ r A a cT^ 

Cabs and Canopies for Underground 
Coal Mining Equipment 

Proceedings: Bureau of Mines Technology Transfer 
Symposium, Charleston, WV, June 22, 1983 



Compiled by William W. Aljoe 




UNITED STATES DEPARTMENT OF THE INTERIOR 
William P. Clark, Secretary 

^ BUREAU OF MINES 

Robert C. Horton, Director 



Library of Congress Cataloging in Publication Data; 




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Bureau of Mines Technology Transfer Symposium (1983 : 
Charleston, WV) 

Cabs and canopies for underground coal mining equipment. 

(Information circular ; 8996) 

Includes bibliographical references. 

Supt. of Docs, no.: I 28.27:8996. 

1. Mining machinery— Safety measures— Congresses. 2. Mine 
railroads- Cars— Safety measures— Congresses. 1. Aljoe, William W. 
II. Title. III. Series: Information circular (United States. Bureau of 
Mines) ; 8996. 



TN2&57tJ4~- [TN3451 622s [622'. 2] 84-600210 



CONTENTS 

Page 

Abstract 1 

Cabs and canopies for low-coal underground mining equipment , by William W, 

Aljoe 2 

Cost benefit analysis for low-coal cabs and canopies, by K. L. Whitehead 20 

Canopy protection for operators of continuous haulage systems in low-seam- 

helght coal, by R. J. Gunderman and A, J. Kwitowski , 31 

ESD low-coal canopy technology, by Jack Mantel 48 

Cabs and canopies for FMC underground coal mining equipment , by Martin D, 

Wot ring 55 

Cabs and canopies for Joy underground mining equipment, by Gary C. Marshall.,.. 61 

Cabs and canopies for Lee-Norse continuous miners, by E. W. Hiltebeitel 68 

Evaluation of "minimum" and "lowest practical" working heights for safe use of 

canopies , by William W. Aljoe 75 

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second 



CABS AND CANOPIES FOR UNDERGROUND COAL MINING EQUIPMENT 

Proceedings: Bureau of Mines Technology Transfer Symposium, 
Charleston, WV, June 11, 1983 

Compiled by William W. Aljoe ^ 



ABSTRACT 

This publication contains eight papers presented at a Bureau of Mines 
Technology Transfer Symposium in Charleston, WV, on June 22, 1983. 
Five of the papers describe the results of Bureau-sponsored research on 
cabs and canopies for low-coal underground mining equipment. The other 
papers describe the efforts of three underground coal mining equipment 
manufacturers (FMC, Joy, and Lee-Norse) in the area of cab and canopy 
design. 



^Mining engineer, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA, 



CABS AND CANOPIES FOR LOW-COAL UNDERGROUND MINING EQUIPMENT 

By William W. Aljoe"" 

ABSTRACT 



This paper reviews the history of 
Federal cab and canopy regulations, the 
problems inherent to the use of canopies 
in low coal, and various technical 
aspects of cab and canopy design. Each 
type of underground face equipment 



covered by canopy regulations is examined 
in terms of the cab and canopy designs 
presently available. Innovative design 
features facilitating machine operation 
in low coal are emphasized. 



HISTORY OF LOW-COAL CANOPY REGULATIONS AND PROBLEMS 



Between 1966 and 1978, 819 fatalities 
occurred because of roof falls^ in under- 
ground mines. Over 500 of these involved 
operators or helpers on the nine major 
types of self-propelled electric face 
equipment — continuous miners, shuttle 
cars, scoops, tractors, ramcars, roof 
bolters, cutters, face drills, and load- 
ing machines. This fatality record indi- 
cated that overhead protection for opera- 
tors of face equipment would be extremely 
helpful. Prior to 1972, however, very 
few machines were equipped with overhead 
operator protection, and these machines 
were used almost exclusively in coal 
seams higher than 72 in. 

Recognition of the potential benefits 
of overhead protection brought about the 
enactment of Federal canopy regulations 
(30 CFR 75-710-1) in 1972. These regula- 
tions specified the deadline dates by 
which cabs and/or canopies would be re- 
quired on the nine types of face equip- 
ment mentioned above. The requirements 
applied immediately to machines used in 
coal seams higher than 72 in; a delayed 
enforcement schedule was adopted for ma- 
chines used in lower coal seams. The 
purpose of this delayed enforcement 

^Mining engineer, Pittsburgh Research 
Center, Bureau of Mines, Pittsburgh, PA. 

^Roof Control Division, Pittsburgh 
Safety Technology Center, Mine Safety and 
Health Administration, Pittsburgh, PA. 



schedule was to allow time for develop- 
ment of cab and canopy technology for 
low-coal machines. 

The beneficial effects of the cab 
and canopy regulations were immediately 
apparent, as canopy "saves" (occasions 
when the presence of the canopy saved a 
worker from death or injury) began to 
occur soon after the regulations were en- 
acted. In the past 10 years, almost 200 
canopy "saves" have been reported to the 
Mine Safety and Health Administration 
(MSHA) . The actual number of "saves," 
however, has probably been much greater 
than this due to underreporting. For ex- 
ample, mines may have hesitated to report 
minor roof falls that were deflected by 
canopies but did not result in signifi- 
cant injury, property damage, or down- 
time. On the other hand, some roof falls 
were so massive that they covered entire 
machines and required extensive cleanup 
and rescue efforts to free operators who 
had been saved by canopies. Witnesses to 
canopy saves of this type were usually 
the strongest proponents of Federal can- 
opy regulations. 

Unfortunately, the presence of cabs and 
canopies can also cause three serious 
problems — "roofing," restricted vision, 
and insufficient space within the opera- 
tor's compartment. "Roofing" (a colli- 
sion between the canopy and an overhead 
obstruction) introduces three potential 



hazards: (1) roof supports (bolts, 
posts, crossbars, etc.) could be damaged, 
weakening the roof stability of the en- 
try; (2) ventilation tubing or electric 
trailing cables hanging from the roof 
could be broken or dislodged, creating a 
fire or explosion hazard; and (3) the 
canopy itself could be knocked off its 
supports and onto the operator. The ob- 
vious solution to roofing would be to 
lower the canopy, but this usually re- 
sults in the other two problems , re- 
stricted operator vision and insufficient 
working space. When these two problems 
occur, machine operators tend to lean be- 
yond the confines of their compartments, 
exposing themselves to collisions with 
ribs, roof, and other obstacles in the 
mining section. 

Cab and canopy problems were especially 
prevalent in low-coal mines for obvious 
reasons; as stated above, this fact was 
acknowledged in the delayed enforcement 
provisions of the 1972 canopy regula- 
tions. However, the length of time al- 
lowed for development of low-coal canopy 
technology proved to be insufficient, and 
the deadline dates for con^)liance were 
postponed three times (in 1973, 1976, and 
1977). The 1977 revision stated that 



canopies would not be required on ma- 
chines operating in mining heights (mine 
floor to unfinished roof) lower than 42 
in, and this exemption for very low coal 
mines still exists today. 

Mine operators, however, continue to 
experience numerous canopy problems in 
coal seams greater than 42 in in height; 
in fact, these problems still occur in 
seams as high as 60 in. The main reason 
for this is that the machines being used 
in 42- to 60-in coal seams were not de- 
signed to allow for the everyday use of 
canopies. Operators' compartments on 
many existing machines are neither long 
enough nor wide enough to allow a com- 
fortable seating position with a low can- 
opy height. Furthermore, machine con- 
trols are often arranged such that the 
operator must sit upright or lean forward 
to reach them. Unfortunately, anthropo- 
metric measurements show that the opera- 
tor must assume at least a semireclining 
posture to remain seated beneath a canopy 
that is low enough to prevent roofing. 
Because of the prevalence of low-coal 
canopy problems , it became obvious that 
innovative designs for low-coal machines, 
cabs, and canopies were needed. 



INNOVATIVE CAB AND CANOPY DESIGNS FOR LOW COAL 



During the past 5 years, numerous at- 
tempts have been made to develop cab and 
canopy designs suitable for low-coal min- 
ing equipment. Many of these designs 
were originated by the equipment manufac- 
turers; however, coal company personnel 
also played an important role in the de- 
sign process. The remainder of this pa- 
per discusses the innovative cabs and 
canopies developed by the mining industry 
to help alleviate the canopy problems in- 
herent to low-coal mines. 

CONTINUOUS MINERS 

Continuous miners have historically 
been involved with more roof fall fatali- 
ties than any other machine type (except 
roof bolters, which will be discussed 
later). Since equipment designers also 



recognized this problem, more design ef- 
fort has been placed on cabs and canopies 
for continuous miners than for most other 
machine types. The need for overhead 
protection on continuous miners was ob- 
viously recognized by mine operating 
personnel; in many cases, problems with 
canopies were tolerated by continuous 
miner operators more readily than by 
operators of other machines. Consequent- 
ly, continuous miners are the machines on 
which cabs and canopies have been most 
successful. 

Figure 1 shows a cab and canopy on a 
continuous miner designed specifically 
for low coal seams. The cab and canopy 
have several innovative low-coal design 
features: 




FIGURE 1. - Split=type floating canopy on continuous miner. 



1, The operator's deck is hinged to 
the miner frame and "floats" or "slides" 
along the mine floor during normal opera- 
tion. This design feature has been 
utilized on almost all recently devel- 
oped low-profile continuous miners. The 
greatest advantage of a "floating" deck 
versus a "fixed" deck is that no ground 
clearance is needed; this allows the can- 
opy top to be lowered by about 6 to 8 in 
without sacrificing operator headroom. 
Another advantage of the "floating" deck 
is that it can drop below the crawler 
level of the miner when tramming over an 
undulation, thus decreasing the likeli- 
hood of canopy roofing. 

2. The canopy top is split into two 
sections; the upper plate covers the 
operator's head and torso, while the low- 
er plate protects the operator's legs and 
the machine controls. The major advan- 
tage of this split-type canopy design is 
that the operator can look through the 
space between the plates to see in the 
forward direction. 



3. The controls on this machine were 
designed to allow the operator to re- 
cline, thus allowing the canopy to be 
placed lower than if the operator were 
forced to sit upright. The tram controls 
are located in the center of the opera- 
tor's deck; since the operator straddles 
them when seated in the deck, they are 
close at hand at all times. The handles 
of the other machine controls extend 
rearward, also placing them within easy 
reach of the reclining operator. 

Figure 2 shows the same basic cab and 
canopy design as figure 1; however, the 
canopy in figure 2 was modified slightly 
to compensate for the effect of the light 
mounted on its outside edge. Although 
this light was needed to achieve compli- 
ance with mine illumination regulations, 
it created a problem because the operator 
was forced to lean outward, far beyond 
the confines of his compartment, to see 
down the side of the machine. Since this 
would have exposed the operator's head to 
collisions with the roof, rib, or other 




FIGURE 2. = Extension welded to outer edge of continuous miner canopy. 



obstructions, the mine mechanics welded 
an extension plate on the outboard side 
of the canopy top. This extension made 
the canopy the widest point on the ma- 
chine, causing it to strike the roof or 
rib before the operator's head did. 

Figure 3 shows a cab and canopy as de- 
signed and installed by coal company 
maintenance personnel when the miner was 
rebuilt in the company's central shop. 
Like the cabs and canopies in figures 1 
and 2, the operator's deck was designed 
to "float" on the mine floor. How- 
ever, this floating deck had another ad- 
vantage — it was hydraulically adjust- 
able. A hydraulic jack connected the 
rear ("floating") end of the deck to the 
rear bumper of the miner, allowing the 
operator to selectively raise or lower 
the deck. The deck is in the raised po- 
sition in figure 3 because the mine floor 
in this area was particularly wet and 
muddy. Another unique feature of this 
operator compartment was that the con- 
trols were adjustable; that is, the con- 
trol handles and valve banks were mounted 



on a pan that could be moved backward and 
forward to accommodate the reach of both 
small and large operators. The pan could 
also be rotated upward to permit the op- 
erator to enter and leave the cab. The 
seat back was adjustable also; in figure 
3, the seat back is in the upright posi- 
tion, but it could easily be tilted and 
locked into a reclining position if the 
operator needed more headroom. Finally, 
the canopy top itself was hydraulically 
adjustable, allowing the operator to ei- 
ther (1) raise it to allow more headroom 
and vision or (2) lower it to prevent 
roofing. The hydraulic adjustment capa- 
bilities of the deck and canopy would be 
especially helpful in areas where the 
vertical clearance changed abruptly be- 
cause the canopy would not always have to 
be fixed at its lowest setting. 

SHUTTLE CARS 

Some of the cab and canopy design fea- 
tures used on continuous miners have also 
been tried on shuttle cars; however, the 
design problems with shuttle cars have 




FIGURE 3. = Hydraulically adjustable continuous miner cab and canopy with adjustable controls. 



been harder to solve because shuttle cars 
must travel faster, farther, and oftener 
than continuous miners. Despite these 
problems, innovative shuttle car design 
features developed in recent years have 
allowed the use of canopies in lower coal 
seams than ever before. For example, 
canopy roofing occurs less frequently if 
the operator's compartment is mounted be- 
tween the tires of the shuttle car rather 
than at the rear end; consequently, al- 
most all shuttle cars intended for low- 
coal use now have center-mounted opera- 
tors' compartments. Shuttle car seats 
have also been improved to provide easier 
machine operation from a reclining posi- 
tion, a necessity if canopies are to be 
successful in low coal. 

Figure 4 shows a low-profile, center- 
driven shuttle car with a "floating" 
operator's compartment. The major dif- 
ference between the "floating" compart- 
ment in figure 4 and the continuous miner 
conyjartments in figures 1-3 is the means 
by which it is attached to the machine. 
Instead of being hinged to the machine 
frame, the shuttle car operator's deck 
is connected to the side of the machine 
through vertical T-shaped guide bars. 



When tramming over rough mine floors, the 
shuttle car compartment moves straight up 
and down rather than in an arc. Again 
the advantage of the "floating" deck is 
that the canopy can be lowered without 
sacrificing operator headroom. 

Unfortunately, when mine floors are 
very wet, rough, or muddy, floating oper- 
ator compartments experience more prob- 
lems than compartments with fixed ground 
clearances. For example, water and mud 
can enter a floating compartment more 
easily than when the deck is raised above 
the mine floor. More importantly, a 
floating deck is more likely to become 
"hung up" in a rough or muddy mine floor, 
reducing the machine's ability to tram. 
Not surprisingly, these problems are 
worse for shuttle cars than for continu- 
ous miners; however, in fair to good bot- 
tom conditions, floating operator com- 
partments have been quite successful on 
both machine types. 

Figure 5 illustrates another problem 
that occurs when canopies are used on 
shuttle cars in low coal, regardless of 
whether the deck floats or is fixed. The 
presence of sideboards often eliminates 




FIGURE 4. = Floating operator's deck on center=clriven shuttle car. 




FIGURE 5. - Operator leaning out of shuttle car cab for better vision. 



operator vision to the opposite side of 
the entry, and the operator's natural re- 
action is to lean outward and upward to 
look over the sideboards. As shown in 
figure 5, the presence of a canopy makes 
this process more difficult and danger- 
ous. Since vision to the opposite side 
of the entry is almost always negligible 
on low-coal shuttle cars, the machine and 



compartment should be designed such that 
the operator can easily see down the side 
of the machine without leaning out beyond 
the canopy, 

A novel concept for improving operator 
vision on shuttle cars is shown in figure 
6; this experimental operator compartment 
was built and tested under a Bureau of 




FIGURE 6. = Canopy mounted on turntable in center of shuttle car operator's compartment. 



Mines contract,^ The major difference 
between the compartment in figure 6 and 
other center-mounted shuttle car compart- 
ments is that the operator does not 
change seats when changing tram direc- 
tions. Instead, the seat is located on a 
turntable in the center of the compart- 
ment, and the operator manually rotates 
the turntable to face forward or back- 
ward. The improvement in vision results 
from the use of a split-type canopy de- 
sign similar to those in figures 1 and 2. 
In the compartment shown in figure 6, 
however, the center portion of the canopy 

•^Kopas, P. Design and Development of 
Protective Canopies for Underground Low 
Coal 48" and Under (contract HOI 8801 4, 
Kogen Industries, Inc.). BuMines OFR 
17-81, 1980, 89 pp.; NTIS PB 81-167533. 



is fixed to the turntable and remains 
above the operator's head and torso as 
the seat rotates. The two lower plates 
are cantilevered from the ends of the cab 
deck to protect the operator's legs and 
the machine controls. 

Figure 7 shows how this canopy design 
improved operator vision; the photogra- 
pher was seated in the compartment in 
figure 6 with the canopy in its lowest 
position. Although vision alongside the 
machine is not available, it is obvious 
that the canopy itself does not inhibit 
vision at all. Furthermore, sideboards 
were not present on this shuttle car, 
which greatly improved vision to the op- 
posite side of the entry. The need for 
the operator to lean dangerously outward 
was greatly reduced. 



Several innovative cab and canopy de- 
sign concepts have been used successfully 
on end-driven shuttle cars. For example, 
floating operators* decks have been suc- 
cessful on end-mounted operator compart- 
ments when good bottom conditions were 



present. However, the most promising cab 
and canopy concept for end-driven shuttle 
cars may be the "transverse" or "side- 
saddle" concept shown in figure 8, It 
has been accepted and praised by shuttle 
car operators as a great improvement in 




FIGURE 7. » Improved vision with split-type canopy on shuttle car. 




FIGURE 8. - Side-saddle tram compartment on end-driven shuttle car. 



10 



both comfort and vision. In transverse 
compartments, the operator faces the 
shuttle car conveyor at all times and 
merely rotates his or her head to see in 
the forward or reverse directions; no 
seat changing is required. The trans- 
verse seat configuration makes it possi- 
ble for the operator to see alongside the 
shuttle car without leaning beyond the 
protection of the compartment. Extra leg 
room is provided by building a tunnel be- 
neath the conveyor discharge boom and 
placing the tram and brake pedals at the 
back of the tunnel. More seating width 
can also be provided with the transverse 
compartment layout. 

SCOOPS, TRACTORS, AND RAMCARS 

Scoops and tractors are widely used for 
both coal haulage and cleanup work in low 
coal because they are smaller, more ver- 
satile, and less expensive than shuttle 
cars or continuous haulage equipment. 
(Ramcars are somewhat similar to scoops 
in design but are used primarily for coal 
haulage.) Although scoop and tractor 



operators are only occasionally involved 
in roof falls, improvements in cab and 
canopy design are needed for these ma- 
chines because of the large number of in- 
juries resulting from collisions with 
the mine roof and ribs. Most models of 
scoops and tractors have transverse oper- 
ator compartments that allow easier vi- 
sion along the side of the machine, but 
the compartments are often too small to 
protect the operator from collisions when 
she or he reclines. The problem is com- 
plicated by the presence of relatively 
simple post-and-plate canopies that se- 
verely restrict operator vision. These 
poorly designed canopies increase the po- 
tential hazard because they introduce 
another object against which the operator 
can be crushed. 

Figure 9 shows a properly designed cab 
and canopy on a scoop; note that the cab 
deck extends far beyond the side of the 
scoop, providing both protection and un- 
restricted vision along its side. Note 
also that the canopy does not interfere 
with operator vision when the compartment 




FIGURE 9. - Operator's deck on scoop extended beyond side of machine. 



11 



is extended in this manner. This ex- 
tended type of compartment is even more 
critical in coal seams lower than 42 in, 
where canopies are not required, because 
it eliminates the need for the operator 
to sit upright, thereby reducing the dan- 
ger of collisions with the roof. 

Operator ingress and egress is another 
common problem on existing scoops and 
tractors. Although the machine design 
itself contributes to this problem, the 
presence of a canopy often makes it 
worse. Figure 10 shows a scoop canopy 
designed to facilitate ingress and 
egress; it is mounted on rollers and con- 
tained within guide rails on the side- 
walls of the operator's compartment. Be- 
fore entering the cab, the operator 
slides the canopy across the machine, 
creating more room for entry. Once 
seated, the operator pulls the canopy 
back into position and locks it in place. 

The operators' compartments on the 
scoops in figures 9 and 10 were located 
at the centers of the machines; fig- 
ure 11 shows an end-driven scoop with 
an improved cab and canopy design. 



(Operators' compartments on most tractors 
are also located at the ends of the ma- 
chines) . The canopy top on this scoop is 
hydraulically adjustable, and the hydrau- 
lic cylinders have been placed to mini- 
mize interference with operator vision. 
The back of the seat can be adjusted to 
allow the operator to recline comfort- 
ably, as in figure 11, or be raised to 
peinnit sit-up operation when the mine has 
sufficient vertical clearance. This is 
the same basic seat design as on the con- 
tinuous miner in figure 3; it was also 
designed by coal company shop personnel. 

ROOF BOLTERS 

Roof bolters are probably the hardest 
types of machines to describe in terms of 
cabs and canopies because of the wide 
variety of roof bolter designs in use to- 
day. The development of automated tem- 
porary roof support (ATRS) systems for 
roof bolters has made the subject of cabs 
and canopies even more complex. This 
paper involves only the tramming station 
of the roof bolter because this is the 
only location where a complete operator 
compartment is required. However, some 



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FIGURE 10. ° Sliding canopy top on scoop for easier ingress and egress. 



12 




FIGURE IL = Hydraulically adjustable canopy on end=driven scoop. 



type of overhead protection must also be 
provided at the drilling station — either 
a canopy, an ATRS, or both. 

Operator compartments on single-head 
roof bolters can be divided into two 
basic types: (1) drill-and-tram compart- 
(2) tram-only compartments, 
most innovative cabs and 
existing single-head roof 
drill-and-tram compartments 
retrofitted to the machines 



On the compartment in figure 12, this 
is accomplished by attaching the deck 



ments and 
Perhaps the 
canopies on 
bolters are 
that were 



(figs. 12-13). These compartments are 
somewhat similar to the continuous miner 
compartments in figures 1-3 because they 
are hinged to the machine frame at one 
end and "float" on the mine floor at the 
other. During drilling and bolting, the 
hydraulic jacks on these cabs and 
canopies are extended vertically as far 
as possible, thus wedging the compart- 
ment between the mine floor and roof. 
When tramming these bolters between 
holes or to and from the face areas, 
the operators can raise the tram decks 
above the floor to prevent them from 
hanging up in rough or muddy areas. 



mechanically to the 
raising the boom, 
on the compartment 
double-acting , 
raised upward 



drilling boom, then 

The hydraulic jacks 

in figure 13 are 

allowing the deck to be 

and suspended from the 



canopy during tramming. The canopy in 
figure 13 is also hinged to the machine 
f rame . 

Note also in figure 13 that an extra 
hydraulic jack is located on the opposite 
side of the drill head from the opera- 
tor's compartment. This jack is con- 
nected to the inboard edge of the canopy 
through a cantilevered arm that extends 
across the drilling boom and behind the 
head. During drilling and bolting, the 
jack is emplaced against the roof to pro- 
vide additional roof support; during 
tramming, the jack is retracted and sus- 
pended from the cantilevered arm. 

Almost all dual-head roof bolters have 
tram compartments that are attached rig- 
idly to the machine at a fixed distance 



13 



above the mine floor. Figures 14 and 15 
show two of the better low-coal tram com- 
partments on existing dual-head roof 
bolters. The compartment in figure 14 is 



located between the tramming wheels on 
the right side of the machine and is 
large enough to allow the operator to as- 
sume a reclining position. However, the 




FIGURE 12. - Floating, hydraulically adjustable canopy on single=head roof bolter. 




FIGURE 13. - Extra safety jack attached to floating, hydraulically adjustable canopy on single- 
head roof bolter. 



14 




FIGURE 14. ~ Long tram deck on duaUhead roof bolter permits reclining operation. 




FIGURE 15. - Extended tram deck and hydraulically adjustable canopy on duaUhead roof bolter. 



15 



operator often has to lean outward to see 
down the side of the machine and must 
turn around and look backward when tram- 
ming in reverse. The compartment in fig- 
ure 15 is mounted transversely and is 
extended beyond the side of the machine 
to improve operator comfort and vision, 
and the canopy top is hydraulically ad- 
justable. The major disadvantage of this 
tram compartment is that it is located on 
the rear corner of the machine, which 
causes the canopy to move farther upward 
in undulating conditions. 

Figure 16 shows one of the few "float- 
ing" tram compartments on dual-head roof 
bolters. This is a rather unique roof 
bolter because it has two operators' com- 
partments, both at the front of the ma- 
chine. The compartment on the left side 
of the bolter (right side of figure 16) 
contains controls for both drilling and 
tramming; the other compartment contains 
only drilling controls. Unfortunately, 
this particular machine was designed for 
medium coal seam heights and does not 
contain a reclining seat to facilitate 
canopy use in low coal. 

CONVENTIONAL MINING EQUIPMENT 

In general, the operators' compartments 
on conventional face equipment — cutters, 
face drills, and loading machines — were 
not designed for low-coal canopy use. 
"Floating" compartments are virtually 



nonexistent, and present compartments are 
usually too short and narrow. Further- 
more, substantial machine redesign would 
probably be needed to provide a suitable 
low-coal cab and canopy configuration. 
For this reason, fewer canopies are used 
on low-coal conventional equipment than 
on most other machine types. 

Cutters and Face Drills 

Figures 17 and 18 show the typical 
operator seating positions when canopies 
are used on cutters (fig, 17) and face 
drills (fig, 18) in low coal. Obviously, 
operator comfort and vision are less than 
adequate. In addition, the machine con- 
trols were designed to accommodate opera- 
tors in an upright, seated position; 
therefore, proper machine operation would 
be difficult even if the compartments 
were long enough to allow the operators 
to recline. Although operator vision 
could be improved somewhat by installing 
the two-post, cantilevered canopy shown 
in figure 19, the basic designs of most 
cutters and face drills would have to be 
altered substantially to allow problem- 
free canopy use in low coal. Fortunate- 
ly, cutters and face drills move rather 
slowly and are not often involved in roof 
falls, so the lack of canopy protection 
in low coal creates fewer hazards than 
the lack of canopies on other machine 
types. 




FIGURE 16. - Dual operator stations at front of dual-head roof bolter. 



16 




FIGURE 17o = Operator cramped within tram compartment on cutting machine. 



Loading Machine s 

Figure 20 shows an operator's position 
while he is seated beneath a canopy on a 
typical low-coal loader — his legs are 
crossed, his neck is bent, and his knees 
nearly touch his chin during "normal" 
operation. This situation is not sur- 
prising considering that the overall de- 
sign of the operator's station on the 
loading machine has not changed substan- 
tially in over 20 years. In fact, many 
of the loaders in use today were origi- 
nally designed for "walk along" opera- 
tion, with cabs and canopies added after 
the machines were built. 

Unlike cutters and face drills, loaders 
are relatively mobile machines and are 
frequently involved in roof falls; there- 
fore, cab and canopy protection in low 
coal is much more critical. For this 
reason, loader operators are more toler- 
ant of "inadequate" cabs and canopies 
than operators of cutters and face 
drills. Several coal companies have made 



improvements on existing loader compart- 
ments while rebuilding the machines 
(e.g. , widening and/or lengthening the 
operators' decks). However, substantial 
machine redesign would be necessary to 
provide a truly workable low-coal cab and 
canopy. 

The Bureau of Mines has sponsored one 
project to achieve an improved cab and 
canopy design for a loading machine.'* 
This project is described in more detail 
on page 48. To install the operator's 
compartment developed under this program 
(fig. 21), significant modifications to 
the loader itself must be made. However, 
if this compartment is installed, it will 
represent a substantial improvement over 
existing loader compartment designs. 



^Mantel, J. Extension of Cab and Can- 
opy Technology to Low Coal Seams. Ongo- 
ing BuMines contract H0387026; for inf., 
contact J. R. Bartels, TPO, Pittsburgh 
Research Center, BuMines, Pittsburgh, PA. 



17 




FIGURE 18. = Operator cramped within tram compartment on face drill. 




FIGURE 19„ = Mockup of two-post canti levered canopy for cutter and face drill. 



18 




FIGURE 20o = Operator cramped within tram compartment of loading machine. 




FIGURE 21o - Mockup of improved loader tram compartment. 



19 



SUMMARY AND CONCLUSION 



Coal mining equipment manufacturers 
have undoubtedly made improvements in 
low-coal cab and canopy design during the 
past 5 years. The designs shown here 
represent a few of the better ideas in- 
corporated into existing machines, but 
none is the ultimate answer to low-coal 
cab and canopy problems . Because of the 



inherent physical constraints of low-coal 
mines, machine operators will always ex- 
perience comfort and/or vision problems; 
however, through equipment redesign and 
efficient use of existing cab and canopy 
technology, the severity of these prob- 
lems can be reduced. 



20 



COST BENEFIT ANALYSIS FOR LOW-COAL CABS AND CANOPIES 
By K. L. Whitehead^ 



INTRODUCTION 



In general, the use of canopies over 
operators' compartments of underground 
coal mining equipment has proven to be 
beneficial as protection against both 
falling roof rock and the operator's head 
striking against projections from the 
roof line. However, experience has shown 
that in lower working heights, particu- 
larly 42 in and lower, existing canopy 
technology can be difficult to apply suc- 
cessfully. In these low-seam height con- 
ditions, there is frequently inadequate 
roof clearance to operate the machines 
and/or the operator compartments become 
too cramped and uncomfortable for per- 
sonnel to function efficiently and safe- 
ly. Because of these problems, MSHA has, 
by policy, suspended enforcement of the 
canopy regulations in seam heights of 
42 in and lower. As a result, accidents 
potentially preventable by the use of 



overhead or lateral 
occurring. 



protection are still 



The Bureau of Mines is, therefore, ini- 
tiating action on a program to develop 
technology that will eliminate, or at 
least minimize, these machine-related ac- 
cidents. However, the Bureau must decide 
whether or not to continue a development 
program for machine-mounted protective 
devices; establish a program to develop 
alternate technology such as remote con- 
trol, robotics, etc.; or fund a program 
including aspects of both technologies. 
A final decision on the type of research 
program to establish must be based on 
several factors, one of which was the 
study conducted by Bituminous Coal Re- 
search (BCR) under the Bureau contract 
"Cost Benefit Analysis of Low Coal Cabs 
and Canopies" and summarized herein. 



PROCEDURE USED IN COST-BENEFIT ANALYSIS 



The general procedure used in the anal- 
ysis was to compare the cost to the coal 
industry of fitting both old and new min- 
ing equipment with protective structures 
to the dollar value assigned to the in- 
juries and fatalities that could have 
been prevented by the use of properly de- 
signed cabs and canopies. In performing 
this analysis, several assumptions and 
qualifying statements were used: 

1. For those accidents considered 
"canopy preventable," the death or injury 
was assumed to have been prevented, not 
just reduced in degree of severity. 



2. Even though adequate low-coal can- 
opy technology is not available, it was 
assumed that canopies could be success- 
fully installed on all equipment regard- 
less of working height. 

3. Philosophically, a dollar value 
cannot be placed on the death or injury 
of a worker. However, for purposes of 
analysis and comparison, a consistent 
method of assigning dollar values to ac- 
cidents had to be used. For the purpose 
of this project, the Accident Cost Indi- 
cator Model (ACIM) developed by MSHA's 
Health Safety and Analysis Center (HSAC) 
in Denver, CO, was selected. 



^Supervising engineer. Bituminous Coal 
Research, Monroe vi lie, PA. 



4. The only ACIM accident analyses 
available to BCR were for the years 



1975-78. It was therefore assumed that 
the average cost calculated for canopy- 
preventable fatal and lost-time accidents 
during 1975-78 could be used to calculate 
a dollar value for preventable accidents 
occurring in the other years of the anal- 
ysis period. 



21 



To carry out the analysis, two sets of 
data had to be developed — the cost to in- 
stall overhead and lateral protective 
structures and the benefits realized from 
the use of these structures. 



COSTS OF INSTALLING CABS AND CANOPIES 



The installation costs were established 
by requesting equipment manufacturers and 
rebuild shops to supply estimates of the 
cost to install these structures on new 
and rebuilt machines. Cost figures for 
six different protective structures were 
requested to reflect equipment designs 
and accident causes. For example, a roof 
bolter would require both a tram canopy 
and a drill-station canopy to protect the 
operator from roof falls and would also 
require side protection to guard against 
injuries from rib rolls or collisions 
with other equipment. Table 1 summarizes 
average installation costs by type of ma- 
chine and protective structure type. A 



comparison of these figures shows that 
retrofitting is generally more expensive 
than new installations, indicating that, 
if possible, the protective structures 
should be included when a new machine is 
ordered. 

Calculation of installation costs to 
the entire industry obviously requires 
knowing the equipment population. Unfor- 
tunately, these statistics are not read- 
ily available, particularly for the peri- 
od after 1978. Since the analysis was to 
cover 1971-80, an estimate of equipment 
population and its distribution with re- 
spect to seam heights had to be made. 



TABLE 1. - Average estimated installation costs and number of cost estimates 
received for protective structures on new and rebuilt equipment 



Equipment type 



Tram 
deck 



Type of protective structure 



Side pro- 
tection 



Tram 
canopy 



Drill 
deck 



Drill 
canopy 



ATRS 



Number of 
estimates 
received 



Continuous miners: 

New. 

Retrofit 

Shuttle cars: 

New 

Retrofit 

Tractors and/or scoops 

New 

Retrofit 

Roof bolters: 

New 

Retrofit 

Cutting machines: 

New 

Retrofit 

Face drills: 

New 

Retrofit 

Loading machines: 

New 

Retrofit 

NAp Not applicable. 



$2,500 
3,886 

3,100 
6,471 

15,000 
19,625 

640 
1,095 

600 
1,000 

486 
48 6 

1,000 
1,750 



$585 
1,060 

435 
765 

278 
278 

302 
352 

610 
1,340 

283 
453 

455 
795 



$2,690 
2,990 

1,568 
1,897 

1,538 
1,961 

2,520 
2,615 

1,300 
2,270 

945 
1,378 

1,500 
2,625 



NAp 
NAp 

NAp 
NAp 

NAp 
NAp 

$717 
1,528 

NAp 
NAp 

NAp 
NAp 

NAp 
NAp 



NAp 
NAp 

NAp 
NAp 

NAp 
NAp 

$4,794 
4,326 

NAp 
NAp 

NAp 
NAp 

NAp 
NAp 



NAp 
NAp 

NAp 
NAp 

NAp 
NAp 

$8,816 
7,866 

NAp 
NAp 

NAp 
NAp 

NAp 
NAp 



12 



10 



22 



The procedure used to develop the popu- 
lation statistics can be summarized as 
follows: 

1. For 1971-78, the population of con- 
tinuous miners, cutting machines, mobile 
loading machines, face drills, and roof 
drills was based on statistics published 
in the National Coal Association publica- 
tion "Coal Data." 

2. Population estimates were made for 
all equipment types during 1979-80, and 
for shuttle cars and scoops for 1971-80. 
These estimates were based on several 
factors, including — 

a. Coal production by mining meth- 
od for each year in the period 1971-78. 

b. The productivity or tons mined 
per cutting machine for continuous and 
conventional mining. 



c. Equipment ratios 
period 1971-78. 



used over the 



d. The ratios of shuttle cars and 
tractors and/or scoops to continuous 
miners and loading machines based on MSHA 
equipment compliance data. 



The resulting population data were 
broken down for each year by equipment 
type used in seam heights of 42 to 48 in 
and 42 in and lower (table 2). 

Establishing the industry cost for in- 
stallation of protective structures re- 
quired that the population data reflect 
annual changes in the number of new ma- 
chines introduced, old machines continu- 
ing to operate, and machines retired. 
This provided a means to estimate the 
annual number of machines requiring in- 
stallation of either new or retrofit 
operator-protective structures. An esti- 
mate of the average machine life for each 
type of face equipment was developed from 
data provided by coal companies and re- 
sulted in estimated machine replacement 
schedules. Table 3 is an example of the 
estimated continuous miner replacement 
schedule for the two seam height ranges 
of interest. 

The installation costs (table 1) were 
then applied to the population data (ta- 
bles 2 and 3) to estimate total costs to 
the industry (table 4). For the analy- 
sis, the machines were assumed to require 
all applicable protective structures 
(lateral and overhead protection). 



BENEFITS OF CAB AND CANOPY PROTECTION 



The second factor in the analysis, the 
"benefits," was calculated using accident 
data obtained from the ACIM file. Since 



data were only available for 1975-78, 
these had to be used to establish a sta- 
tistical basis for classifying accidents 



TABLE 2. - Equipment population as a function of seam heights 
of 43 to 48 and <42 in 





Continuous 


Cutting 


Mobile 


Face 


Roof 


Shuttle 


Tractors 


Year 


miners 


machines 


loaders 


drills 


bolters 


cars 


and) 

SCO( 


/or 




43-48 


<42 


43-48 


<42 


43-48 


<42 


43-48 


<42 


43-48 


<42 


43-48 


^42 


3pS 




43-48 


<42 


1971 


178 


338 


288 


617 


248 


454 


329 


506 


300 


573 


694 


625 


430 


1,180 


1972 


185 


351 


265 


567 


235 


431 


298 


459 


308 


589 


684 


618 


424 


1,165 


1973 


187 


354 


215 


460 


242 


443 


232 


358 


313 


597 


699 


630 


433 


1,187 


1974 


196 


372 


212 


455 


258 


473 


266 


410 


416 


794 


740 


667 


458 


1,259 


1975 


220 


418 


223 


478 


206 


379 


281 


432 


407 


777 


694 


630 


430 


1,187 


1976 


236 


449 


252 


541 


198 


364 


295 


454 


440 


840 


707 


642 


438 


1,211 


1977 


268 


508 


209 


448 


190 


348 


265 


408 


507 


967 


746 


676 


462 


1,275 


1978 


282 


536 


200 


430 


170 


313 


237 


364 


491 


938 


736 


670 


456 


1,265 


1979 


312 


593 


195 


417 


162 


298 


231 


356 


530 


1,013 


772 


704 


479 


1,327 


1980 


342 


650 


18 6 


399 


151 


277 


221 


341 


570 


1,088 


803 


732 


498 


1,381 



23 



TABLE 3. - Continuous miner replacement schedule, 1971-80 





Original machines 




Replacement machines 




New 




Total 


Machines 


Year 


(1971 


and older) 


+ 


(added 


after 


1971, 


+ 


machines 


= 


machines 


retired 










but not 


new machines) 












SEAM HEIGHT < 42 in 


1971 




363 
















363 


40 


1972 




323 


+ 









+ 


54 


= 


377 


40 


1973 




282 


+ 




54 




+ 


45 


^ 


381 


41 


1974 




242 


+ 




99 




+ 


59 


= 


400 


40 


1975 




202 


+ 




158 




+ 


89 


= 


449 


40 


1976 




161 


+ 




247 




+ 


75 


:= 


483 


41 


1977 




121 


+ 




322 




+ 


103 


= 


546 


40 


1978 




81 


+ 




425 




+ 


70 


= 


576 


40 


1979 




40 


+ 




495 




+ 


103 


^ 


638 


41 


1980 







+ 




598 




+ 


101 


= 


699 


40 










SEAM HEIGHT 


43 TO 48 


in 










1971 




153 
















153 


17 


1972 




136 


+ 









+ 


23 


= 


159 


17 


1973 




119 


+ 




23 




+ 


18 


=s 


160 


17 


1974 




102 


+ 




41 




+ 


25 


= 


168 


17 


1975 




85 


+ 




66 




+ 


38 


= 


189 


17 


1976 




68 


+ 




104 




+ 


30 


= 


202 


17 


1977 




51 


+ 




134 




+ 


45 


= 


230 


17 


1978 




34 


+ 




179 




+ 


29 


= 


242 


17 


1979 




17 


+ 




208 




+ 


42 


= 


267 


17 


1980 







+ 




250 




+ 


43 


= 


293 


17 



TABLE 4. - Cost to industry to install cabs and canopies 
on face equipment, 1971-80^ 





Seam height 


Equipment type 


42 in and lower 


43 to 48 in 




Retrofit 


New 


Retrofit 


New 


Continuous miners. ••••••••• 


$2,880,768 
3,033,380 
1,281,301 
2,528,130 

27,133,224 
6,612,292 
9,278,192 


$4,036,725 
409,130 
267,384 
523,035 

19,203,872 
2,704.590 

16,562,934 


$764,951 

933,709 

509,647 

869,956 

5,856,928 

3,912,577 

2,825,782 


$1,692,075 
153,110 


Cutting machines 


Face drills 


13*^ ■'64 


Loading machines 


244.380 


Tractors and/or scoops 

Shuttle cars 


5,633,360 
2.184.084 


Roof bolters 


6,927,406 


Total 


52,747,287 


43,707,670 


15,673,550 


16,944,879 


Total cost by seam height.. 


$96,454,957 


$32,618,429 



' Based on 
shops. 



1981 dollar value as supplied by manufacturers and rebuild 



and assigning dollar values to accidents 
in other years of the analysis peri- 
od. This was based on the assumption 
that the percentage of cab-or-canopy pre- 
ventable accidents, grouped by seam 
height and type of equipment involved, 
did not change significantly from year to 
year. 



Nonfatal disabling and fatal accidents 
of all types numbered in the thousands 
during the 1975-78 period, but certain 
parameters were established by BCR to 
limit the accidents included in the anal- 
ysis to those potentially preventable 
with overhead or side protective struc- 
tures. These parameters were — 



24 



1. Machine type - the study included 
only those machines covered under the cab 
and canopy regulations. 

2. Degree of injury - only fatalities 
and "lost-day" accidents were included. 

3. Type of accident - only accidents 
involving haulage operations , face ma- 
chinery, or falls of roof, rib, or face 
were included. 

4. Mine worker activity - only such 
activities as roof bolting-drilling, op- 
erating shuttle car, operating continuous 
miner, etc., where a cab or canopy could 
have been helpful, were included. 

5. Cost of accident - only those acci- 
dents with costs of at least $1,000 were 
included. Accidents costing less than 
$1,000 represented 32 pet of the number 
of accidents but only 0.5 pet of the to- 
tal cost. 

Review of the ACIM information resulted 
in the selection of 616 accidents to be 
included in the analysis. These were 
grouped into 11 categories, based on the 



need for tram decks, side protection, 
overhead protection, and combinations of 
these structures (table 5). Grouping the 
accidents in this manner emphasized the 
type of protective structure that would 
prevent the most accidents. The 616 ac- 
cidents were also grouped according to 
seam height and equipment type, as shown 
in table 6. 

TABLE 5. - Classification of "cab or 
canopy preventable" accidents 



Class 



Type of protection required 



1 Tram deck only. 

2. Side protection only. 

3 Tram canopy only . 

4 Tram deck and canopy. 

5 Tram deck and side protection. 

6 Tram deck, side protection, and 

canopy, 

7 Drill station deck only. 

8 Drill station canopy only. 

9 Drill station deck and canopy. 

10 ATRS system only. 

11 ATRS system and drill station 

canopy. 



TABLE 6. - "Cab or canopy preventable" injuries (1975-78), grouped 
by equipment type, preventability classification, and seam height 



Equipment type 


Preventability classification 




1 


2 


3 


4 


5 


6 


1 


8 


9 


10 


11 


Total 




SEAM HE 


IGHT 


<42 


! In 
















Continuous miners 

Cutting machines 


2 
3 
1 
2 

1 

3 


12 
4 
1 
9 

14 

32 

8 


35 

3 
4 
45 
39 
9 






1 
1 

1 






1 

2 


1 







1 









2 








88 

















39 








6 


49 
8 


Face drills 


5 


Loading machines ......... 


18 


Tractors and/or scoops... 
Shuttle cars ............. 


61 
73 


Roof bolters 


156 


Total 


12 


80 


135 


3 


4 


1 


2 


88 





39 


6 


370 


S 


EAM HEIG 


HT 43 


TO 


48 


in 














Continuous miners 

Cutting machines 





1 


2 


10 
1 

1 
3 
5 
24 
3 


16 
1 
2 
5 
17 
43 
7 







1 




2 


1 

1 

1 


1 


1 


1 










76 


























15 








5 


27 
4 


Face drills .............. 


3 


Loading machines 


11 


Tractors and/or scoops... 
Shuttle cars 


22 
70 


Roof bolters 


109 


Total 


3 


47 


91 


1 


5 


3 


76 








15 


5 


246 



25 



Since the cost benefit analysis covered 
a 10-year period (1971-80), some method 
had to be developed for estimating the 
preventable accidents that occurred dur- 
ing the years not included in the ACIM 
data, i.e., 1971-74 and 1979-80. The de- 
velopment of this information was based 
on (1) the accident-injury reports in 
the MSHA publications and (2) the assump- 
tion that the percentage of preventable 
injuries, grouped by seam height and type 
of equipment involved, does not change 
significantly from year to year. The 



estimated number of preventable accidents 
by year, seam height, and type of equip- 
ment is summarized in tables 7 through 
10. Tables 7 and 8 cover nonfatal dis- 
abling injuries; tables 9 and 10 cover 
fatalities. 

The cost associated with the accidents 
was handled in two ways. For 1975-78, 
the costs calculated by the ACIM system 
were available and were used as the "ben- 
efit" for the analysis. For 1971-74 and 
1979-80, the benefits were calculated 



TABLE 7. - Number of preventable nonfatal injuries in 42-in and 
lower seam heights, 1971-80 



Equipment type 


1971 


1972 


1973 


1974 


1975 


1976 


1977 


1978 


1979 


1980 


Total 


Continuous miners. 


10 


12 


9 


7 


8 


12 


13 


13 


16 


17 


117 


Cutting machines.. 


2 


2 


2 


1 





1 


1 


6 


3 


3 


21 


Face drills 


2 


1 


1 


1 


1 


1 


1 


2 


2 


2 


14 


Loading machines . . 


3 


4 


3 


3 


4 


6 


5 





5 


5 


38 


Tractors and/or 
























s coops 


10 
16 


11 
17 


9 
16 


7 
11 


9 

17 


9 
18 


14 
19 


12 
17 


15 
25 


15 
25 


111 


Shuttle cars 


181 


Roof bolters 


32 


36 


32 


22 


27 


36 


47 


37 


52 


50 


371 


Total 


75 


83 


72 


52 


66 


83 


100 


87 


118 


117 


853 



TABLE 8. - Number of preventable nonfatal injuries in 43- to 48-in 
seam heights, 1971-80 



Equipment type 


1971 


1972 


1973 


1974 


1975 


1976 


1977 


1978 


1979 


1980 


Total 


Continuous miners. 


5 


7 


6 


4 


7 


6 


8 


6 


9 


10 


68 


Cutting machines.. 


1 


1 


1 


1 


1 


2 





1 


1 


1 


10 


Face drills 


1 





1 


1 





1 


1 


1 


1 


1 


8 


Loading machines . . 


3 


3 


2 


1 


7 


2 





1 


4 


3 


26 


Tractors and/or 
























s coops ........... 


3 


5 


4 


3 


3 


5 


5 


6 


7 


7 


48 


Shuttle cars 


15 


17 


14 


11 


18 


15 


25 


10 


24 


24 


173 


Roof bolters 


23 


25 


23 


16 


35 


25 


29 


17 


37 


36 


266 


Total 


51 


58 


51 


37 


71 


56 


68 


42 


83 


82 


599 



TABLE 9. - Number of preventable fatal injuries in 42-in and 
lower seam heights, 1971-80 



Equipment type 


1971 


1972 


1973 


1974 


1975 


1976 


1977 


1978 


1979 


1980 


Total 


Continuous miners. 
Cutting machines.. 

Face drills 

Loading machines.. 
Tractors and/or 
scoops 


2 




8 

1 
3 


1 


1 

6 

3 


1 



1 

5 

3 





1 

4 

1 
2 





1 

5 

1 
3 


1 


1 

4 
1 
3 







2 




2 



1 

6 

3 


1 


1 

5 

1 
3 


1 




5 

2 


9 



7 

50 


Shuttle cars 

Roof bolters 


5 
25 


Total 


14 


11 


10 


8 


10 


10 


2 


12 


11 


8 


96 



26 



TABLE 10. - Number of preventable fatal injuries in 43- to 48-in 
seam heights, 1971-80 



Equipment type 


1971 


1972 


1973 


1974 


1975 


1976 


1977 


1978 


1979 


1980 


Total 


Continuous miners. 



































Cutting machines.. 



































Face drills 



































Loading machines.. 


1 














1 











1 


3 


Tractors and/or 
























scoops. .......... 





1 


1 


1 





1 


1 


1 


1 





7 


Shuttle cars 





2 





1 





1 


1 








1 


6 


Roof bolters 


2 


1 


1 


1 


2 


1 





1 


1 


1 


11 


Total 


3 


4 


2 


3 


2 


4 


2 


2 


2 


3 


27 



TABLE 11. - Estimated benefits paid for injuries preventable 
with cabs and canopies, 1971-80 



Equipment type 


Seam height 




42 in and below 


43 to 48 in 


Total 


Continuous miners 

Cutting machines 

Face drills 


$5,760,969 

234,944 

147,000 

4,677,948 

28,376,958 

6,653,080 

15,624,840 


$1,553,181 

61,500 

119,200 

1,771,500 

5,181,442 

7,066,855 

12,536,535 


$7,314,150 
296,444 
266,200 


Loading machines 

Tractors and/or scoops. 
Shuttle cars 


6,449,448 
33,558,400 
13,719,935 


Roof bolters 


27,801,375 


Total 


61,115,739 


28,290,213 


89,405,952 



using the average cost, by machine type, 
for "fatal" and "nonfatal disability" 
accidents during 1975-78. For 1971-80, 



the estimated "benefits," by machine type 
and seam height, are summarized in 
table 11. 



COST-BENEFIT RATIOS 



The cost-benefit ratio is simply the 
industry cost to install protective 
structures divided by the "benefits" — 
that is, the accident costs that could 
have been averted by the use of these 
structures. The calculations were made 
for two periods — 1971-80 and 1975-78. 
The calculated ratios, along with the, 
corresponding cost and benefit values, 
are summarized in tables 12 and 13. Two 
analyses were conducted because — 

1. The 4-year study more accurately 
reflects the "benefit" factor since the 
values come directly from the ACIM 
program. 

2. The 10-year study takes into ac- 
count machine replacement experience, 
and, therefore, more realistically 



spreads the installation costs over the 
machine life. The cost-benefit ratios of 
the 10- and 4-year studies are very simi- 
lar and show that the loading machine has 
the most favorable cost-benefit ratio, 
while the cutting machine has the least 
favorable. This indicates that from the 
standpoint of providing maximum personnel 
protection per dollar spent on protective 
structures, highest priority should be 
given to further development of protec- 
tive structures for loading machines. On 
the other end of the scale, the cost of 
protective structures per dollar of ben- 
efit is so high for cutting machines 
that continued development of current 
technology would seem inappropriate 
and alternate technology should be 
considered. 



27 



TABLE 12. - Cost-benefit ratios for installing cabs and canopies, 1971-80 



Equipment type 



Cost of installing 
cabs and canopies 



Accident benefits 
paid 



Cost-benefit 
ratio 



SEAM HEIGHT <42 in 



Continuous miners ...•..•.••••••• 


$3,679,517 

1,831,122 

823,768 

1,622,960 

24,647,391 
4,955,788 

13,742,280 


$5,760,969 

234,944 

147,000 

4,677,948 

28,376,958 

6,653,080 

15,264,840 


0.63 


Cutting machines ....* •••••• 


7.79 


Face drills •«••«•••••••••••••••• 


5.60 


Loadinff machines ......•••••••••• 


.34 


Tractors and /or scoods. ...•••.•• 


.86 


Shuttle cars 


.74 


Roof holers 


.90 


Total or average 


51,302,826 


61,115,739 


.83 



SEAM HEIGHT 43 TO 48 in 




Continuous miners .....•..•.•••.. 


$1,306,928 

578,095 

340,378 

582,200 

6,111,855 

3,242,904 

5,187,866 


$1,553,181 

61,500 

119,200 

1,771,500 

5,181,442 

7,066,855 

12,536,535 


0.84 


Cuttinff machines •.....•.••...... 


9.40 


Face drills ...*...........•..*.. 


2.85 


Loading machines ................ 


.32 


Tractors and/or scoops .......... 


1.17 


Shuttle cars 


.45 


Roof bolters 


.41 


Total or average 


17,350,228 


28,290,213 


.61 



TABLE 13. - Cost-benefit ratios of installing cabs and canopies, 1975-78 



Equipment type 



Cost of installing 
cabs and canopies 



Accident benefits 
paid 



Cost-benefit 
ratio 





SEAM HEIGHT <42 In 






Continuous miners 


$2,554,859 

1,253,010 

617,763 

1,122,000 

17,947,738 
4,033,336 
9,536,577 


$1,982,900 
89,500 
52,500 
1,999,100 
9,706,000 
2,645,800' 
5,598,600 


1.28 


Cutting machines 


14.00 


Face drills 


11.76 


Loading machines 


.56 


Tractors and/or scoops 


1.84 


Shuttle cars 


1.52 


Roof holers 


1.70 


Total or average 


37,065,286 


22,074,400 


1.67 



SEAM HEIGHT 43 TO 48 in 




Continuous miners ............... 


$868,792 

455,861 

269,410 

400,646 

4,212,989 

2,546,180 

3,284,567 


$616,700 

24,600 

44,700 

599,100 

2,207,700 

2,429,700 

4,636,500 


1.40 


Cutting machines 

Face drills ..................... 


18.53 
6.02 


Loading machines •.....••«....•.. 


.66 


Tractors and/or scoops .......... 


1.90 


Shuttle cars 


1.04 


Roof holers 


.70 


Total or average 


12,038,448 


10,559,000 


1.13 



ESTABLISHING RESEARCH PRIORITIES 



The final decision on what technology 
to pursue and which machine should 
receive priority should not be based on 
the cost-benefit ratio alone. Seven fac- 
tors were identified as relevant to the 
future direction of the Bureau's cab and 



canopy research program (tables 14-15). 
These seven factors varied in impor- 
tance among different machine types; for 
example, the loading machine had the 
lowest cost-benefit ratio, so it would 
be the preferred research target if the 



28 



cost-benefit ratio were the only criter- 
ion used to assign research priorities. 
However, preventing a fatality or very 
serious injury would also be a desirable 
goal; since the tractors and/or scoops 
were involved in more "canopy prevent- 
able" fatalities and severe injuries than 
any other machine type, they would be the 
preferred target if the Bureau's main 
goal were to prevent only these types of 
accidents. Tractors and/or scoops would 
also be the preferred target if the Bu- 
reau's goal were to address the most pop- 
ular low-coal machine; however, the roof 
bolter would receive highest priority if 
the machine population trend were consid- 
ered most important. 

Therefore, the seven different machine 
types considered in this analysis were 
ranked for each of the seven factors 
that could influence Bureau research pri- 
orities. Tables 16 and 17 show the re- 
sults of this ranking procedure; for each 
factor, the machine type demanding the 
greatest amount of attention was ranked 
number 1, and the type demanding least 
attention was ranked number 7. Note that 
tables 14 and 16 cover machines in seam 
heights of 42 in or less; tables 15 and 



17 show the rankings obtained for ma- 
chines in 43- to 48-in seams. An overall 
"average" ranking was then calculated for 
each equipment type, with the low numbers 
again corresponding to the machine de- 
serving the highest priority. 

In addition, each factor was ranked ac- 
cording to its importance in the overall 
analysis (bottom row of tables 16 and 
17). The ranking of the factors was not 
included in the calculation of the over- 
all average but could be used to estab- 
lish priority for two or more machines 
with the same or very similar ranking. 
For example, in 42-in and lower seams, 
the "average ranking" criterion would 
give continuous miners, tractors and/or 
scoops, and bolting machines equal prior- 
ity. However, considering only the top- 
ranked factor, preventable fatal injury 
population, tractors and/or scoops would 
be the top-priority machines. The analy- 
sis for 43- to 48-in seams identified the 
roof bolter as the top-priority machine 
according to the "average ranking" cri- 
terion; again, tractors and/or scoops 
ranked first in terms of preventable fa- 
tal injuries. 



CONCLUSIONS AND RECOMMENDATIONS 



The final decision to continue or dis- 
continue cab and canopy development for 
any face-equipment type will depend on 
(1) the cost-benefit ratios considered 
to be the lower and upper limits for 
justifying the expenditures required 
to continue cab and canopy development 
and (2) the ranking given the seven pa- 
rameters used to prioritize, by equip- 
ment type, the need for development of 
operator-protection technology. Since 
decisions on these two items may depend 
on factors not considered in this 
analysis, only the following general 
recommedations for the continued develop- 
ment of cab and canopy technology can be 
made: 

1. There is an immediate need to de- 
velop some type of operator-protection 



technology, particularly for continuous 
miners, tractors and/or scoops, and roof 
bolters in seam heights of 48 in and 
lower. 

2. In seams 42 in and lower, the high- 
er cost-benefit ratio values generally 
indicate that future cab and canopy de- 
velopment is marginally justified. In 
view of past experience with attempts to 
use canopies in these seam heights, BCR 
recommends consideration of alternate 
technologies. 

3. For 43- to 48-in coal seams, where 
canopies have been used successfully, the 
cost-benefit ratio values indicate that 
further development of canopy technology 
is warranted. 



29 





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31 



CANOPY PROTECTION FOR OPERATORS OF CONTINUOUS HAULAGE SYSTEMS 

IN LOW-SEAM-HEIGHT COAL 

By R, J. Gunderman^ and A, J. Kwitowski2 



ABSTRACT 



Placing an operator of a mobile contin- 
uous haulage conveying system under a 
protective canopy was investigated using 
the latest technology for both canopies 
and floating compartments. Investiga- 
tions first considered how to position 
the operator in the low compartments and 
included unobtrusive observation of human 
subjects repositioning themselves when 
confined to the compartment. Locations 
for such a compartment on the crawler- 
mounted machine were considered using 
both small-scale and full-scale mockups. 

A floating operator compartment was de- 
signed in conjunction with the new design 



for an improved machine. Evaluation of 
the compartment for human factors was 
made at the manufacturer's facility prior 
to installing the machine in an under- 
ground coal mine. Subjects representing 
the male 5th, 50th, and 95th percentile 
sizes were used along with photographic 
techniques for recording data. 

Operation of the new machine with oper- 
ator compartment in a coal mine with seam 
heights typically between 40 and 46 in 
was monitored for 10 months. The practi- 
cal feasibility of this operator protec- 
tion was adequately demonstrated for coal 
seams as low as 40 in. 



INTRODUCTION 



This program was one of several ini- 
tiated by the Bureau of Mines to investi- 
gate the applicability of canopies and 
cabs to coal mining machines operating in 
seam heights below 48 in. A study con- 
tract was awarded to the Jeffrey Mining 
Machinery Division, Dresser Industries, 
Inc. , to investigate the feasibility of 
placing the operator of a model 506C-5 
double-bridge carrier, shown in figure 1, 
under a protective canopy. This crawler- 
mounted carrier supports a bridge con- 
veyor on the inby end (seen to the left 
of the operator) , which is linked to 
the discharge boom of the continuous min- 
ing machine. A similar bridge conveyor 
links between the carrier and the pan 
line. If there are more than three en- 
tries, a second bridge carrier and an 
additional bridge conveyor may be added 
to lengthen the reach. The operator of 

^Consultant; formerly project manager, 
Jeffrey Mining Machinery Division, 
Dresser Industries, Inc., Columbus, OH. 

^civil engineer, Pittsburgh Research 
Center, Bureau of Mines, Pittsburgh, PA. 



the double-bridge carrier maneuvers the 
machine to follow movements of the mining 
machine and controls operation of the 
conveyor. This machine is used in seam 
heights as low as 28 in. 

The inby bridge conveyor is supported 
on a carriage or dolly that rides on the 
receiving conveyor of the double-bridge 
carrier. This carriage, which is free 
to move approximately 6 1/2 ft, provides 
flexibility for small movements of the 
continuous miner. The operator of the 
double-bridge carrier must move the car- 
rier to assure that the carriage is ade- 
quately positioned to allow movement of 
the continuous miner in either direction. 

Using technology and ideas applied in 
previous Bureau of Mines contracts as 
well as concepts developed by manufac- 
turers and coal companies, the feasibil- 
ity of a protective operator compartment 
was investigated. As shown in figure 1, 
the controls on the 506C-5 are on the 
side (or fender) , and the operator usual- 
ly squats or kneels next to the machine. 



32 




FIGURE 1. = Operator at controls of 506C=5 double-bridge carrier. 



This gives the operator good visibility 
and mobility. However, this position is 
vulnerable in the event of a roof fall or 
if the bridge carrier is inadvertently 



pushed by the mining machine, which could 
possibly pinch the operator against a 
rib. 



ACKNOWLEDGMENT 



The work described in this paper was 
performed under Bureau of Mines contract 
H03870273 to the Jeffrey Mining Machinery 
Division, Dresser Industries, Inc., Co- 
lumbus, OH. The in-mine evaluation was 



performed under a cooperative agree- 
ment between the Solar Fuel Co., Somer- 
set, PA and the Jeffrey Mining Machinery 
Division. 



PRELIMINARY DESIGN 



All possible operating positions for 
the human body were considered because 
of the severe space restrictions in low 
seams. Studies were conducted on six 
subjects to evaluate each one's response 
to postures within the confines of a 
compartment 30 in high, 24 in wide, and 

^Gunderrnan, R. J. Canopy Technology 
for Low Seam Continuous Haulage. Final 
Report USBM Contract No. H0387027, Feb. 
1980, 72 pp.; for inf., contact A. J. 
Kwitowski, TPO, Pittsburgh Research Cen- 
ter, BuMines, Pittsburgh, PA. 



70 in long. A video camera recorded 
their positions and movements on tape for 
later analysis. Each subject was told 
to position himself in the compartment 
and to go through simulated functions 
of operating controls and observing both 
inby and outby operation for periods of 
1 h. These subjects tried lying down, 
squatting, sitting cross legged, sit- 
ting in a very reclined position, etc. , 
and needed frequent postural relief. 
The consensus favored the reclined seat 
position. 



33 



Required dimensions for an operator 
compartment were thus determined to be 
approximately 5-1/2 ft long and at least 
2 ft wide in the shoulder area, A de- 
tailed consideration of the 506C-5 bridge 
carrier showed that there was no possi- 
bility of locating such an operator com- 
partment on that machine. However, Jef- 
frey was starting design of a new bridge 
carrier with increased haulage capacity 
and greater tram speed. Effort was then 
directed at locating an operator compart- 
ment on the new machine so that the re- 
sulting design would allow adding the 
compartment, if desired. Fender-mounted 
controls would be retained in the stan- 
dard design because of mine operator 
preference, especially in seam heights 
less than 36 in. 

Many potential locations for the com- 
partment on the machine were examined 
using a small-scale model. Because of 
the requirement for frequent ingress and 
egress, along with maintaining a proper- 
ly located machine center of gravity. 



the side-rear compartment position was 
preferred. 

A full-scale mockup was constructed 
from cardboard and wood (fig, 2), Only 
significant portions of the bridge car- 
rier were Included in the mockup since 
it was used primarily to determine opera- 
tor fit, functional movement, and visi- 
bility. The canopy on the mockup and 
the items inside the operator compartment 
were moved until satisfactory locations 
were established empirically. Figure 3 
shows a 50th percentile operator in the 
mockup. 

Results from the mockup evaluation 
showed feasibility with canopy heights 
adjustable between 30 to 42 in above the 
floor. Depending upon seam conditions 
and undulations , a bridge carrier of this 
type could operate in seams from 48 to 36 
in high. Jeffrey agreed to constrain the 
design of the new machine to allow for 
this compartment as an option. 



OPERATOR COMPARTMENT DESIGN 



Considerable effort went into the de- 
sign of the operator compartment and at- 
tachment to the bridge carrier. Also, 
the controls of the new bridge carrier 
were relocated to the right side of the 
machine instead of the left side because 
the operator of the continuous mining ma- 
chine is on the right side. The result- 
ing design is shown in figure 4. 

The newly designed machine is 9 in 
wider and almost 4 ft longer than the 
506C-5 in order to accommodate the com- 
partment and the fact that the outby 
conveyor must swing as much as ±90°. 
This also required longer crawler 
tracks. Therefore, the compartment has 
to float on the floor in order not to im- 
pede mobility. 

The operator compartment is attached to 
the main frame by two pivots with hori- 
zontal axes. Figure 5 is a closeup of 
this attachment taken during tests for 
mobility. The compartment side of the 



pivots consists of steel collars that 
slide vertically on the two front canopy 
support posts. This slide travel is lim- 
ited to 8 in by the support members at 
the bottom and fixed collars on top. 
Angular movement of the compartment is 
limited with respect to the discharge 
conveyor in the upward direction by a 
stop on the conveyor and in the downward 
direction by a link chain. 

Selection of an operator seat was lim- 
ited by the practical factor of avail- 
bility. In this case a seat was selected 
that has a seat unit separate from the 
back rest. A new adjustable seat mount 
was designed using data from the func- 
tional mockup evaluation. A single lever 
on the seat back retracts dual pins that 
engage in holes in the seat mount. This 
provides positions reclining from the 
vertical of 25°, 34°, 43°, 51°, or 60°. 
A similar arrangement allows separate 
adjustment of the seat cushion to angles 
from the horizontal of 10°, 20°, or 



34 




FIGURE 2. = Looking down on the mockup from the receiving end. 



35 




FIGURE 3o - Operator seated in the mockup. 




FIGURE 4. - Completed operator compartment on new machine. 



36 




FIGURE 5. - Attachment of compartment to mainframe. 



30°. The adjustment holes are Indicated 
by arrows in figure 6. The mount with 
the seat slides forvard and back on the 
track bar shown in figure 7. A clevis 
pin through holes in the seat mount al- 
lows nine fore and aft position selec- 
tions in 1-in increments. 

Arm rests that tilt back for ingress 
and egress were provided. However, the 
left arm rest was deleted when it was 



found to interfere with both arm movement 
and other items in the compartment. 

As noted in figure 1, the operator 
kneeling and facing the machine only has 
to turn 90° to see either inby or outby 
operation. Unfortunately, there is not 
enough room in the entries to place a 
compartment so that the operator faces 
the machine the same as with the 506C-6. 
The compromise in the new design is to 



37 




FIGURE 6. - Seat adjustment. 




FIGURE 7. = Seat fore-aft adjustment track. 



38 



place the operator at a small angle (19°) 
with respect to the longitudinal axis of 
the machine. This angle helps consider- 
ably when turning the head to see the 
outby transfer point. Most operators, 
sitting in the reclining position, roll 
the body slightly off the seat when turn- 
ing to see outby. 

Four posts are used to support the can- 
opy because of the size and loads. The 
posts telescope, and each is adjustable 
with a pin for canopy heights from 30 to 
42.5 in in 2.5-in steps. During the com- 
partment design phase, the Solar Fuel Co. 
became interested in this program and 
agreed to an in-mine evaluation of the 
machine at its mine No. 9. Because the 
seam heights there have considerable var- 
iation, as well as undulations, they de- 
sired a method to change canopy height 
without the need for extra equipment, 
such as a jack. Two hydraulic lift cyl- 
inders were added, one at the left rear 
as shown in figure 8 and the other at the 
opposite corner. A small pump with oil 




FIGURE 8. - Operating the canopy adjusting pump 
and flow valve. 



reservoir and a reversing valve comprise 
the rest of the canopy raise system. The 
pump is operated by stroking the handle, 
and the flow direction is set by the 
valve. The first step in adjusting the 
canopy height is to pump up the circuit 
to lift the weight of the canopy off the 
four pins so that they may be removed. 
The four adjustment pins must all be re- 
placed for the desired height setting be- 
fore the operator enters the compartment. 
Figure 9 shows, left to right, the sup- 
port post, raise cylinder, flow direction 
valve, and hydraulic pump. 

Both the electrical and hydraulic con- 
trols are located to the left of the 
operator so as not to impede ingress and 
egress. Figure 10 is a side view of the 
operator compartment taken during the in- 
mine evaluation. Note that the arm rest 
is tilted back. The handhold on the com- 
partment floor adjacent to the seat aids 
the operator during ingress and egress. 

Operator visibility in order to safely 
and comfortably accomplish all functions 
was a major concern. This was investi- 
gated using the full-scale mockup shown 
in figure 2. Markers indicating the 
height above the floor were placed at 
four locations — the inby end of the 
bridge conveyor loading boom, the inby 
ends of both the right and left crawlers, 
and the outby end of the conveyor dis- 
charge boom. Data were collected for 
each size operator in the mockup with 
canopy heights of 30, 32, 34, and 36 in, 
and at each key direction from his eye 
location. Higher canopy settings were 
considered to be no problem, so data were 
not collected for these. Visibility at 
the loading boom, discharge boom, and 
near-side (left) crawler positions for 
the minimum canopy height was 17, 25, and 
25 in respectively. The minimum visible 
height across from the operator and in 
front of the right crawler ranged from 24 
to 35 in. As the canopy was raised, so 
also was the operator's head, which gave 
a lower minimum visible height. 



39 




FIGURE 9. = Canopy adjusting system. 




FIGURE 10. - Side view of operator compartment. 



40 



Variations in the highest visible 
height were relatively small. These var- 
iations were dependent upon how the oper- 
ator positioned the seat, both in angle 



and in fore-aft direction. The highest 
visible measurements ranged from 38 to 50 
in at the four aforementioned positions. 



EVALUATION PRIOR TO SHIPMENT 



These visibility measurements were 
repeated for the actual machine before 
shipment to the mine. As shown in figure 
11, the operator compartment was located 
on the right rather than the left side 
(fig, 2) of the machine. A camera was 
positioned at the operator eye location, 
and pictures were taken of the visibility 
of the inby loading boom position. With 
the canopy set at 30 in above the floor 
(fig, 12), the limits of visibility were 
34 to 47 in. When the canopy was raised 
to 35 in (fig, 13) , the visibility range 
was 23 to 56 in; at a canopy height of 40 
in (fig, 14) , the visibility range was 22 
to 75 in. 

When the operator looks back at the 
bridge carrier outby transfer point, the 
angles are limited. However, the opera- 
tor does not have to see over a large 
vertical angle, as long as the coal flow- 
ing across the transfer point is within 
the visible angle. In figure 15 the lim- 
its are 14 to 34 in with the canopy at 30 
in. In this case the discharge end boom 
was lowered to the floor. The boom can 



be raised 7° or lowered 6° with respect 
to the mainframe, but if the seam height 
requires the canopy at 30 in, it is not 
likely that the boom would be raised more 
than 12 in from the conditions shown in 
figure 15, 

Another visibility consideration is to- 
ward the general outby direction when 
tramming the system outby. In this case, 
the operator will usually turn in the 
opposite direction, as when observing the 
outby conveyor transfer. There is very 
little visibility obscuration in that di- 
rection. However, as shown in figure 16, 
the operator has to strain somewhat even 
with the canopy at 35 in. 

In general, the visibility is reason- 
able at most canopy heights, except for 
30 in. If the operator size is not much 
over the 50th percentile rank and the 
mine conditions are good, then operation 
with the canopy at 30 in should be possi- 
ble. Table 1 summarizes the visibility 
data collected with subjects in the ma- 
chine before shipment to the mine. 




FIGURE 11. - New machine ready for human 
factors evaluation. 




FIGURE 12. 
opy height. 



Looking forward under 30=in can- 



41 




FIGURE 13. - Looking forward under 35-in can- FIGURE 14. - Looking forward under 40-in can- 

opy height. opy height. 




FIGURE 15. = Looking at outby transfer point 
under 30-in canopy height. 



FIGURE 16. - Operator under 35=in canopy 
tramming outby. 



42 






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Canopy heights at 35 in or more appear 
reasonable on this particular mobile 
bridge carrier. The effective window is 
large enough for good visibility angles. 
A perspective on this window may be ob- 
tained from figure 17, which is a photo- 
graph looking at the 5th percentile oper- 
ator in the compartment with the canopy 
set at 35 in. 

A large operator finds the compartment 
a tight fit, as shown in figure 18. This 



subject's favorite position for his legs 
was crossed and on the floor. In this 
scene, the canopy height is 40 in and the 
backrest angle is 34° from the vertical. 
Another view of this operator position is 
shown in figure 19. Note that he uses 
the headrest to support his shoulders 
rather than his head. 

Control operation is primarily with the 
left hand. As shown in figure 20, there 
are four levers located in a console on 




FIGURE 17. - Looking at operator under 35-in can- 
opy from inby end of loading boom. 




FIGURE 18.= Large=s ize operator with legs crossed. 





FIGURE 19. - Large^size operator supporting 
shoulders with headrest. 



FIGURE 20. - Closeup of controls in compartment. 



44 



the floor of the compartment to the left 
of the operator. These levers work hy- 
draulic levers on the mainframe in front 
of the operator through cables. The two 
upper levers are for the left and right 
tram. Pushing them forward moves the ma- 
chine inby, and pushing them rearward re- 
verses the tram. 

There are two lower controls on this 
console that work the receiving and 
the discharge conveyor booms. The left 
control raises the discharge conveyor 
when it is pushed up and lowers it when 
pushed down. The receiving conveyor 



works similarly with the right control 
lever. 

The electrical controls, also shown in 
figure 20, are all located within the en- 
closure mounted high on the left wall of 
the operator compartment. This was an 
existing control box used on another ma- 
chine which had already been approved by 
MSHA. The fire extinguisher is located 
below the electrical control case, and 
the actuator knob is visible just above 
the backrest. Note that the panic bar 
must be operated either with the left 
shoulder or a hand. 



IN-MINE EVALUATION 



The in-mlne evaluation was conducted 
through the cooperation of the Solar Fuel 
Co. at its mine No. 9 near Somerset, PA. 
Seam height at this mine generally ranges 
from 40 to 46 in but frequently pinches 
down much lower. Entries and crosscuts 
are 20 ft wide. Moisture, roof, and 
floor conditions were fair. 

The new bridge carrier (Jeffrey model 
5010) with operator compartment was sub- 
stituted on an operating section for a 
Jeffrey model 506C-5 bridge carrier. The 
new machine was installed early in Octo- 
ber 1981, and the evaluation was planned 
to last 3 months. This time was extended 
for various reasons, including unrelated 
interruptions to the mining operation. 
The bridge carrier with operator compart- 
ment was removed from the mine in October 
1982 and was delivered to the Bureau's 
Pittsburgh Research Center. 

In the section area, the mine operator 
first tried the 35-in canopy setting 
but settled on 37.5 in soon afterwards. 
As can be seen in figure 21, there was 
little clearance between the canopy and 
the roof when the height was set at 37.5 
in. During the in-mine operation, the 
compartment floated well on the floor 
through the action of the slides and piv- 
ots. As a result, the canopy-to-roof 
clearance could be nominally as low as 6 
in. 



Visibility for the operator was fairly 
good with the canopy at 37.5 in. A pro- 
tective metal mesh, angled inward, was 
added to the top of the compartment wall 
to assure that the operator did not reach 
beyond that wall and become pinched by 
the relative movements between the com- 
partment and the discharge conveyor. 
This mesh did not significantly block 
visibility toward the opposite side of 
the machine. 

As stated earlier, the discharge con- 
veyor may be raised several inches. Fig- 
ure 22 is a view from the left front of 
the machine with the conveyor raised to 
the roof. While this conveyor would ob- 
scure vision directly across the machine, 
it does not otherwise affect operation. 
The conveyor would normally be lower when 
tramming the machine, and the operator 
would be able to see through the mesh and 
across the machine. 

Four different operators of the double- 
bridge carrier were observed during 
the in-mine evaluation. One male opera- 
tor was in the 50th percentile size 
range, and two other males were somewhat 
smaller. The other operator was female 
and was slightly larger than a 50th per- 
centile female. 

Operator indoctrination occurred quick- 
ly, although it took the operators some 



45 




FIGURE 21. - Clearance under roof with canopy at 37.5 in. 



time to get over the restless reaction 
that resulted from confinement within the 
compartment. Inability to directly see 
the inby conveyor carriage was the big- 
gest problem. The movement between stops 
on the new machine is only 5 ft, which 
means that the operator must be even more 
skillful in moving the bridge carrier to 
avoid banging the carriage against the 
stops as a result of continuous miner 
movement. The operator seated in the 
conqjartment can only see the top of this 
carriage. 

Each operator had different preferences 
on positions within the compartment. Re- 
positioning was frequent in order to re- 
tain reasonable comfort. There was a 
tendency toward operator inattention 
since the workload within the compartment 
was small. Operator personnel were en- 
couraged to get out of the compartment 
frequently when not running coal and to 
do spillage cleanup, machine inspection, 
etc, , in order to overcome boredom. 



The attitude of the operators varied as 
they became more familiar with the new 
compartment. At first, they did not like 
the concept and were very uneasy because 
they could not move around as they did 
before and because visibility was now re- 
stricted. After familiarization for a 
few weeks, the operators expressed satis- 
faction with the compartment. However, 
the satisfaction did not last long as 
boredom set in and their personal per- 
formance tended to deteriorate. The 
operator workload was subsequently ad- 
justed by having the operators leave the 
compartment when not running coal and 
perform duties including spillage cleanup 
and machine lubrication. Ultimately, the 
operators accepted the operator compart- 
ment as a compromise from the older ma- 
chine with fender-mounted controls. 

Difficult mining conditions, due to 
incursions of stone into the coal seam, 
precluded a good measure of the ef- 
fect that the addition of an operator 



46 




FIGURE 22o - Looking at compartment from left side with conveyor raised. 

compartment on the double-bridge carrier data collected that the production rate 
had on coal production. It appears from is unchanged, 

CONCLUSIONS 



The program objective of investigating 
the feasibility of providing operator operating position, 
protection on crawler-mounted continuous 
haulage systems was achieved. These 
findings are summarized as follows: 



6. A reclining seat provides the best 



7, Operator repositioning within the 
compartment occurs frequently. 



1, Adding operator protection requires 
considerable compromise. 



8, The operators always set the can- 
opy to the highest tolerable setting. 



2. An operator compartment is reason- 
able for seam heights as low as 40 in, 

3. Operation in seam heights as low as 
36 in is questionable and should be eval- 
uated in-mine, 

4. Adding an operator compartment re- 
quired redesign of the machine, 

5. The floating concept using slides 
and pivots works well. 



9, Line of sight to the continuous 
mining machine operator is more frequent- 
ly obscured, 

10, Operators react mostly on the ba- 
sis of familiarity with running condi- 
tions and seldom use signals, 

11, Noted shortcomings with the com- 
partment include — 



47 



Inattention due to minimal 
activity. 

Limited visibility requires ex- 
tra care when tramming. 



It is recommended that the double- 
bridge carrier with operator compartment 
be further evaluated under in-mine condi- 
tions where the mining height is typical- 
ly 36 in. 



Large operators are not practi- 
cal at lowest canopy setting. 



48 



ESD LOW-COAL CANOPY TECHNOLOGY 
By Jack Mantel^ 



INTRODUCTION 



This paper highlights the work per- 
formed by ESD Corp. under Bureau of Mines 
contract H0387026, Development and As- 
sessment of New and Existing Canopy Tech- 
nology to Lower Coal Seams . 

While cab and canopy technology is well 
established for coal mines with working 
heights of over 48 in, technological ad- 
vances are needed for use of cabs and 
canopies in lower working heights. Ac- 
cording to the February 1975 issue of 
Coal Mining and Processing, many mining 
fatalities caused by rib and roof fail- 
ures could be avoided through use of cabs 
and canopies. Figure 1 shows the effect 
on reported fatalities of the 1969 Fed- 
eral Mine Health and Safety Act, which 
required substantially constructed cabs 
and canopies on all self-propelled elec- 
tric face equipment in underground coal 

^ ESD Corp., San Jose, CA. 



mines. 2 These statistics emphasize the 
importance of improving upon the state of 
the art in low-coal canopy technology. 

Four of the programs conducted by ESD 
for the Bureau of Mines included develop- 
ment of cabs or canopies: 

o Inherently Safe Mining Systems. 

o Development of a Dual-Boom, Semiau- 
tomated Roof Bolter. 

o Fabrication and Evaluation of Opti- 
mized Operator Compartments. 

o Development and Assessment of New 
and Existing Technology to Lower Coal 
Seams . 



^Coal Mining and Processing, February 
1975. 



20 



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100 


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Z) — 


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/%^ V 



'%<9 '%5 



/Sx. fS^^ <9> 







/ 



FIGURE 1. - Coal mine fatalities, 1966-74. 



49 



The objective of our current program 
was to develop two transverse-mounted 
canopies, one to be used on an FMC 6L 
shuttle car, and one to be used on a Joy 
14BU10-11A loader. As shown in figure 2, 
an operator sitting in a transverse- 
mounted canopy faces in a direction 90° 
to the direction of travel. The shuttle 



car canopy (fig. 3) was to be used in 
working heights of 42 to 48 in, and the 
loader canopy (fig. 4) was to be used in 
working heights as low as 42 in. This 
paper emphasizes work performed on the 
shuttle car canopy, because evaluations 
have been conducted of its performance in 
an underground mine. 



CONCEPT DEVELOPMENT 



ESD's initial program work was an in- 
vestigation of the state of the art in 
canopy technology to establish design 
needs. On the basis of this investiga- 
tion, concept drawings were prepared, and 
various concepts for shuttle car and 



loader canopies were compared and evalu- 
ated by BCR, the Bureau of Mines, MSHA, 
and mining equipment manufacturers. 
Wooden mockups were made of the selected 
shuttle car and loader canopy concepts: 




FIGURE 2. - Mockup of transverse-mounted canopy for shuttle car. 



50 




FIGURE 3. - Transverse shuttle car canopy layout. 



o A transverse-mounted, floor-riding 
canopy for an FMC 6L shuttle car. 



o A transverse-mounted canopy 
Joy 14BU10-11A loading machine. 



for 



Mockups of seats and other equipment 
were installed in these canopies. Three 
seating configurations were considered. 
The first configuration, with the opera- 
tor seated in a cross-legged position, 
was considered uncomfortable. The sec- 
ond configuration, which offered a seat 
which swivelled 35° from side to side, 
was not considered compatible with the 
transverse-mounting concept. The third 
configuration, which had a sling seat 
which pivoted slightly either forward or 
backward for adjustment and seated the 
operator with his legs slightly bent and 
his feet and lower legs in a tunnel ex- 
tending below the car body, was consid- 
ered the most comfortable and responsive 
to transverse canopy requirements. 



The mockups were evaluated on the basis 
of the following criteria: 

o Suitability for operators ranging 
from a 5th percentile female to a 95th 
percentile male. 



o Maximum inside dimensions. 

o Reach envelopes for 
placement. 



control 



o Seat design, 

o Vision. 

o Ease of ingress and egress. 

o Operator comfort. 

Recommendations resulting from this 
evaluation were incorporated into the 
canopy design. 



51 




FIGURE 4. - Transverse loader canopy layout. 
SHUTTLE CAR CANOPY DESIGN 



ESD's shuttle car canopy, shown in fig- 
ure 5 on FMC 6L shuttle car, has the fol- 
lowing design features: 



Transverse Mounting . — Seating the op- 
erator in a position facing at 90° to the 
direction of shuttle car travel elimi- 
nates the need for the operator to change 
seats when changing from inby to outby 
tram and thus leave the protective can- 
opy. Also, the canopy provides better 
protection from rib bursts or ribbing 
than conventional canopies. 

Floor Riding . — Allowing the canopy to 
ride on the mine floor reduces the hazard 
of roofing associated with end mounted 
canopies. The canopy bottom is flat and 
curved upward on all four edges , giving 
it a sled contour to facilitate moving 
over the mine floor. This sled contour 
also keeps material on the mine floor 
from entering the canopy. 

Canopy float (floor-riding capability) 
has been provided by the addition of 



vertically mounted channels on the inby 
and outby sides of the canopy, which 
interface with guide roller assemblies 
mounted to the car body sides. Two guide 
roller brackets interface with each chan- 
nel to guide the canopy as it rides up 
and down over the floor. 

Pivoting Operator Seat . — The operator's 
seat is composed of heavy canvas fabric 
18 in wide and supported by a pivoting 
strong back. The fabric forms a sling 
which is adjusted by pivoting the strong 
back forward, positioning the operator up 
and forward, or pivoting it backward, po- 
sitioning the operator down and back. 
The operator sits with his legs slightly 
bent and with his feet and approximately 
8 to 10 in of his lower leg in the tunnel 
area (fig. 3). This tunnel extends below 
the car body and conveyor boom and houses 
the brake master cylinder and operating 
pedal and the tram switch and foot actu- 
ation pedal. The operator's left foot 
actuates the brake pedal, and the tram 
switch is actuated by a pedal that pivots 



52 




FIGURE 5. - Transverse operator compartment on FMC 6L shuttle car. 



about a vertical centerline. The shuttle 
car moves in the direction of tram pedal 
rotation. 

Easily Reached Controls . — All controls 
are within easy reach of the operator 
while in his normal sitting position. 



Improved Operator Vision . — Because of 
the transverse mounting of the canopy, 
the operator can see both inby and outby 
without leaving the canopy and changing 
seats. He also has roof-to-floor vision 
without extending his head outside the 
canopy. 



SHUTTLE CAR REWORK 



To provide room for the canopy tunnel 
and its upward movement, the following 
car body rework was performed: 

1. The car body was notched to provide 
clearance for the canopy tunnel and its 
upward movement. 

2. An extension was added to the outby 
side of the outby fender to keep mud from 
being thrown into the cab by the wheel. 

3. Doubler plates were added to com- 
pensate for loss of car body strength due 
to notching. 

Rework was performed on the conveyor 
boom as follows: 



2. The conveyor side plate bottom edge 
was cut out on the canopy mount side to 
accommodate the canopy tunnel and its up- 
ward movement. 

3. The space for the conveyor flight 
return support was reduced by raising the 
conveyor return guiding side plates. 

4. Cable troughs were mounted to the 
side surfaces of the conveyor vertical 
plate. These channels doubled as guides 
for the conveyor flights and were added 
to clean coal from a valley that was cre- 
ated in the conveyor top plate when it 
was raised. 



1. The top plate of the conveyor was 
raised approximately 3 in over that used 
in the standard FMC 6L design. 



53 



UNDERGROUND EVALUATION OF THE SHUTTLE CAR CANOPY 



An evaluation of the shuttle car canopy 
was successfully performed at a Virginia 
Crews Coal Co. (VCCC) mine. VCCC is a 
drift entry coal mining operation with 
seven mines, all located in a 5-square- 
mile area in West Virginia. VCCC oper- 
ating personnel and management were 
extremely cooperative throughout the 
evaluation process. 

The evaluation site was a conventional 
mining operation with a seam height aver- 
aging 52 in. The roof in this mine is 
bolted, and the floor is relatively dry 
and pitching at approximately 4 pet. 
Working height is approximately 48 in. 
During the evaluation, a Goodman loader 
was used to retrieve the coal at the face 
and load either the shuttle car or a 
scoop. The load was then trammed to the 
feeder-breaker. Some ribbing of the can- 
opy occurred, especially when tramming at 
an intersection. Time for a complete cy- 
cle was approximately 4 min, with 40 s 
each utilized in loading and unloading. 

Initial reaction to the shuttle car 
canopy was mostly favorable. The follow- 
ing comments were particularly positive: 

o Smooth ride. 

o Comfortable seat. 



o Roomy canopy . 

o Easy ingress and egress. 

o Good vision inby and outby. 

o Easy orientation to steering. 

o No difficulty with pivoted, foot- 
operated tram switch. 

o No change in sitting position re- 
quired when changing between inby and 
outby tram. 

The following were recommended for 
improvement: 

o Seat sling adjustment. 

o Coal entering the canopy at floor 
level on the entry side when moving into 
position to unload at the breaker. This 
problem was corrected by adding 6-in-high 
plate on the entry side. 

o Coal entering by the opening in 
front of the operator. This problem was 
corrected by adding an expanded metal 
shield over the opening. 

Figure 6 shows the shuttle car compart- 
ment after these improvements were made. 



RECOMMENDATIONS FOR FUTURE WORK 



Floor-riding canopies offer the most 
effective use of available head room 
space, and development of this concept 
should be continued. For lower working 
heights, efforts should be made to extend 
the tunnel farther under the shuttle car 
body. The operator would then be in a 
layback position, and more of his legs 
would protrude into the tunnel. A de- 
crease of 10 in in canopy height could be 
achieved. 

An evaluation site for the loader can- 
opy shown in figure 4 has not yet been 
located. This loader canopy was designed 



for use in 39-in headroom. Its suspen- 
sion system, as designed, consists of 
captured pivot pins on top, a horizontal- 
ly mounted adjustable spring suspension 
on the bottom, and a shock-absorbing ra- 
dius arm. This suspension system permits 
upward, downward, or sideways movement of 
the canopy when roofing or ribbing. This 
resiliency minimizes damage to the struc- 
ture and loader attach points and mini- 
mizes impact on the operator. This load- 
er canopy offers significant improvements 
over the state of the art in low-coal 
canopy technology. 



54 




FIGURE 6. - Final configuration of shuttle car compartment. 



55 



CABS AND CANOPIES FOR FMC UNDERGROUND COAL MINING EQUIPMENT 

By Martin D, Wotringl 

ABSTRACT 



A low-seam canopy has been developed 
by FMC Corp. to be used on scoops and 
shuttle rams. It also can be adapted to 
other equipment. A midseam roof bolter 
has been developed with built-in canopy 
protection. This machine features the 



operator compartment in the center of the 
machine where tramming and bolting can 
be done under the protection of the can- 
opy. Cabs and canopies used on other 
roof bolters and shuttle cars are also 
discussed. 



INTRODUCTION 



The 1969 Coal Mine Health and Safety 
Act required the installation of can- 
opies on face equipment. Initially, many 
coal miners were opposed to these cano- 
pies, which were being retrofitted on 
existing underground equipment. As more 
and more lives were saved, most of this 
opposition vanished. However, operators 
of equipment used in very low seams still 



experienced canopy problems , so MSHA sub- 
sequently revised the canopy regulations 
to exclude all machines used in mining 
heights under 42 in. Equipment manu- 
facturers, rebuild facilities, and coal 
miners have since tried many different 
methods of developing protection for the 
operators. 



ROOF BOLTERS 



Figure 1 shows the standard cab and 
canopy configuration on a model 300 roof 

^Lead engineer, roof bolters, FMC 
Corp., Mining Equipment Division, Fair- 
mont, WV. 



bolter. The canopy covers a tramming 
deck on the side of the machine and the 
drilling station at the front. The orig- 
inal operator's deck was lengthened and 
widened to allow the operator's position 
to be lower, and the tram valve was 




FIGURE 1. - Standard cab and canopy on model 300 roof bolter. 



56 



placed outside the deck to allow more 
room for the operator. The canopy in 
figure 1 was designed to work in seam 
heights from 34 in up. 

Figure 2 shows "floating" aperator's 
deck with a canopy on a model 3000 roof 
bolter. This deck was located beside the 
drill boom where the operator can tram 
the machine as well as install the bolt. 
The "floating" deck allowed the machine 
to be built in a lower package. This ma- 
chine was intended for use in seams 32 in 
and up. 



The cab and canopy configuration on the 
model 370 roof bolter (fig. 3) positions 
the operator in the center of the unit. 
Tramming and bolting are done under the 
protection of the canopy. This machine 
is intended for use in coal seams 6 ft 
and up. 

Dual-head roof bolter models are avail- 
able with canopies over the drill station 
similar to the canopies on the single- 
head bolter in figure 1 and the opera- 
tor's deck (fig. 4). These canopies are 
basically designed for 42 in and above. 



SHUTTLE CARS, SCOOPS, AND SHUTTLE RAMS 



The canopy for the center-driven model 
5L (fig. 5) has four posts, which can be 
mechanically or hydraulically operated. 
The canopy for the end-driven model lOL 
shuttle car (fig. 6) has only three 
posts, to provide better operator vision. 
These machines are intended for use in 
seams of 42 in and up. 

A "low-coal canopy" designed for scoops 
and shuttle-rams is mounted in a track 
which allows it to roll from over the 
operator (fig. 7) to a position over 
the frame of the machine (fig. 8). 
By sliding the canopy back over the ma- 
chine frame, entering and exiting the 



operator's deck is made easier. This 
canopy is mechanically adjustable, locks 
open or closed, and is easily installed 
on other equipment. 

Another protective feature used on 
scoops and shuttle rams in low coal is a 
"glancer." When the coal seam is so low 
that the operator cannot look over the 
top of the machine, the operator will 
lean out of the deck and look along the 
side of the machine. As a form of pro- 
tection from the ribs, the "glancer" is 
added to the outer edge of the operator's 
deck. 



57 




FIGURE 2. - Floating operator compartment on model 3000 roof bolter. 




FIGURE 3. - Model 370 roof bolter with central operator platform and canopy. 



58 




1^^ 



t 



FIGURE 4. » Tram compartment on dual-head roof bolter (model 3510). 




FIGURE 5. - Model 5L shuttle car with center-mounted cab and canopy. 



59 




FIGURE 6. = End-driven shuttle car (model lOL) with three-post canopy. 




FIGURE 7. - Low-cool scoop with sliding canopy in closed position. 



60 




FIGURE 8. - Low-coal scoop with sliding canopy in open position. 



61 



CABS AND CANOPIES FOR JOY UNDERGROUND MINING EQUIPMENT 
By Gary C. Marshall'' 



INTRODUCTION 



In early 1971, the first operator's 
protective canopies were designed for Joy 
mining equipment. Since then, more than 
370 different cab and canopy designs have 
been produced. Many more were on the 
drawing board but never reached produc- 
tion. More than 5,000 cabs and canopies 
have been shipped to Joy's customers over 
the past 10 years. This paper shows the 
evolutionary process in developing cabs 
and canopies on Joy underground mining 
machines. 

Joy's first protective canopies were 
fabricated from plate and pipe such that 



the top structures were reinforced with 
ribs , making them much deeper than pres- 
ent designs, which use flat plate tops 
without ribs. The early structures (fig. 
1) were very strong, but visibility was 
adversely affected and extra headspace 
was used by the pipes or ribs. This is 
not a serious problem when operating in 
high seams; however, many machines oper- 
ating in seam heights of less than 5 ft 
required lower compartments with thinner 
canopy sections. Reinforcing ribs were 
still used, and adjustable height columns 
became popular. 



CONTINUOUS MINERS 



It is difficult to predict exactly how 
much clearance is required between a 
continuous miner canopy top and the low- 
est objects on a mine roof. For exam- 
ple, continuous miners tip up and down 
on their center of gravity when moving 
over an undulating floor, causing some 
unexpected problems. A typical miner 
with a 44-in-high, fixed canopy requires 
15 in of clearance to operate on a trans- 
ition from level ground to a 10° down- 
slope in a 59-in-high seam. However, 
figure 2 shows that the same miner needs 
22 in of vertical clearance to oper- 
ate on a change from level to a 15° 
slope, so the seam height must increase 
to 66 in to keep the canopy from strik- 
ing the mine roof. Lowering the can- 
opy height does not change the clear- 
ance requirements, but it does permit 
working in a lower seam. If the canopy 
height in figure 2 is lowered to 33 in, 
a 10° slope can still be safely traversed 
if the seam height is 48 in (15-in verti- 
cal clearance required). The 15° slope 
can be negotiated (22-in required clear- 
ance) if the minimum seam height is 55 in 
and the canopy height is 33 in. 

^ Joy Manufacturing Co., Franklin, PA. 



Early Joy cabs and canopies for contin- 
uous miners were usually rigid box struc- 
tures surrounding the operators. Some- 
times adjustable columns were used to 
provide easy height changes as the mining 
conditions varied. When the fixed can- 
opies were "roofed" owing to rolls and 
bumps in the floor, as in figure 2, de- 
signers proposed floating compartments. 
Joy believes that floating compartments 
provide the best features for low seams. 
The canopies on Joy's floating compart- 
ments have either three or four adjust- 
able columns and solid plate tops for 
good visibility and maximum safety. Some 
operator cabs have side, or rib, protec- 
tion for high-seam mining applications. 
Others have MSHA-approved face lighting 
systems. 

In very low-seam heights, a split-level 
top on a floating compartment provides 
good visibility on a lower height machine 
such as the 14CM miner shown in figure 3. 
The canopy top in figure 3 is vertically 
adjustable in three different positions. 
Joy's lowest continuous miner, the 15CM 
(fig. 4) , has a 23-in-high chassis and a 
30-in-high operator's compartment (fig. 
5). Since most 15CM miners are operated 



62 




FIGURE 1. - Rib-reinforced canopy on Joy shuttle car. 



55" 



^Center of gravity 





Center of gravity 
FIGURE 2. - Upward movement of continuous miner canopy in undulating conditions. 



63 




FIGURE 3. = Floating cab and split-level canopy on model 14CM continuous miner. 




FIGURE 4. - Overall viev/ of model 15CM continuous miner. 



64 




FIGURE 5. - Operator compartment on model 15CM continuous miner. 




FIGURE 6. - Wooden mockup used to design continuous miner cabs. 



65 



by remote control and do not have opera- 
tors riding on the miner, Joy developed 
the compartment in figure 5 specifically 
for particular customers. Fitting the 
operator, the controls, and all other 
necessary items within a 30-in cab height 
was a very difficult design job. 

Full-scale wooden models (fig. 6) are 
essential to producing successful, inno- 
vative cabs and canopies, especially for 
lower height designs. The wide vari- 
ety of controls and options require the 
use of mockups to evaluate the loca- 
tions for each device. Product managers. 



designers, field engineers, and customers 
all have an input into the detailed de- 
sign process. Many months of work are 
required before an actual compartment is 
built, but the result is a sound enclo- 
sure with a high chance of success. 

Joy also manufactures continuous mining 
machines with integral roof bolters and 
temporary roof support (TRS) cylinders. 
The TRS safety posts are set against the 
mine roof before a bolter operator pro- 
ceeds to the drilling-bolting area just 
in front of the miner operator. 



SHUTTLE CARS 



Most of Joy's shuttle car cabs and can- 
opies have the unobstructed flat plate 
tops. Figure 7 shows the cab and canopy 
on an end-driven shuttle car, and figure 
8 shows a center-driven machine. The ex- 
panded metal screen next to the conveyor 
side of the compartment in figure 7 pre- 
vents spillage on the operator and keeps 
the operator from inadvertently squeez- 
ing an arm or finger between the elevat- 
ing conveyor and the canopy top. Over 
the years, pin-adjustable canopy posts 
have replaced screw-adjustable and fixed 
columns because the screws were diffi- 
cult to operate if the posts were bent 
or the screws became corroded. Joy's 
most popular shuttle car canopies today 



provide for pin adjustments in 2- and 
4-in increments. 

Floating compartments have been devel- 
oped for shuttle cars operating in lower 
seams. Figures 9-11 show recently de- 
signed floating compartments on center- 
driven 21SC shuttle cars. Several of 
Joy's customers are operating floating 
units like these, and more cars are on 
order. The floating decks have well- 
rounded, beveled bottom edges to prevent 
plowing of the mine floor while tramming. 
Smooth, positive cab mounting slides are 
needed so the compartment floats freely 
without binding. 



SUMMARY 



Compared to the last decade, it 
is doubtful that Joy will produce as 
many new cab and canopy designs dur- 
ing the next 10 years. However, it is 



anticipated that improvements in opera- 
tor's controls, comfort, visibility, and 
safety will continue. 



66 




FIGURE 7. - End-mounted cab and canopy on Joy shuttle car. 




-FIGURE 8. - Center-mounted cab and canopy on Joy shuttle car. 



<% .t»i««»<~3«WS?'W».«^5«^®«SS«M?!-«^^«S^ 




FIGURE 9. - Prototype floating cab on center-driven shuttle car. 



67 




FIGURE 10. = Modified floating cab on center-driven shuttle car (side view). 




FIGURE 11. - Modified floating cab on center-driven shuttle car (end view). 



68 



CABS AND CANOPIES FOR LEE-NORSE CONTINUOUS MINERS 
By E. W. Hiltebeitell 



INTRODUCTION 



The design of a cab or canopy for a 
continuous miner is subject to many out- 
side influences in addition to the seam 
height to be considered. In the ideal 
case, the operator's area is considered 
from the inception of the machine design. 
In the case of the Lee-Norse LN 800 con- 
tinuous miner, it was possible to begin 
cab design essentially at the beginning 
of the machine design, starting with con- 
sultation of outside sources and human 
factors specialists. The initial design 



sketches developed into mockups and later 
into prototype machines and finally into 
the production design being sold today. 
The results of this development have af- 
fected many other designs in Lee-Norse 
continuous miners. This paper reviews 
the process that was used on the LN 800 
and shows how a design can evolve over 
the course of a long development pro- 
gram. It also discusses some of the cab 
and canopy developments for low-height 
miners. 



DESIGN PROCESS 



The design process of the operator's 
area for the LN 800 began with the deci- 
sion to improve the cab early in the ma- 
chine design process. Such a decision 
must be accepted by management and shown 
to offer a true market advantage. The 
earlier the cab design is started, the 
more likely that a good design will be 
developed. One of the factors is choos- 
ing space for the operators before it has 
been allocated to other components or de- 
vices on the machine. This space must be 
determined by considering other machine 
parameters, including the length of the 
machine, the width of the machine, height 
restrictions, and type of machine in- 
volved — in this case, a continuous miner 
(fig, 1), One important factor in a con- 
tinuous miner is the distance from the 
operator to the face, or the front of the 
machine. This effectively determines the 
safe and legal depth of cut and has a di- 
rect effect on productivity and safety 
since a deeper cut allows more continuous 
operation before place change. The major 
consideration, however, is operator size. 
The cab should be designed to be compati- 
ble with the size range from 5th percen- 
tile females (smaller individuals) to 



^Product design engineer^ 
Company, Pittsburgh, PA, 



Lee-Norse 



95th percentile males. If such consider- 
ations are used, the cab should be com- 
fortable for 90 pet of the population 
using the machine. 

The next decision involves the general 
design approach. For example, the cab 
could be designed completely in-house, it 
could be totally subcontracted to outside 
consultants or specialist organizations, 
or a combined approach could be used. 
The combined approach can offer the best 
of both worlds; however, it requires di- 
plomacy, tact, and careful consideration 
of the relations between the manufac- 
turer's staff and the consultant's staff, 
In-house design can be quicker and less 
costly, if staff is available. Outside 
design avoids "tunnel vision" or the "not 
invented here" syndrome, but usually 
costs more in initial cash outlay. If 
consultants are to be used, the selection 
process is extremely important. The con- 
tract should be definite about the time 
frame for the work, the work to be done, 
and the acceptable form of the final re- 
port or design. 

For the design of the LN 800 cab, we 
chose the combined approach, Phillip 
Stevens Associates of Skaneateles, NY, 
was chosen since they had a number of 



69 




Cab 

PLAN VIEW 



\ 
\ 




1 




K 

\ 




1 


/ 



Canopy 



59.8 
50.8' 




63.5" 



^^^^^^^^^^;^^^^^^^^^^^^^^^^^^^^^^^^^^%^^^^^;^^^^ 



397' 



ELEVATION 
FIGURE 1. - Layout drawing of LN 800 continuous miner. 



successful design and human factor proj- 
ects for Ingersoll-Rand Corp. In the 
initial meetings with Phillip Stevens 
Associates, Lee-Norse attempted to define 
the space available, the specific compo- 
nents that could not be changed (and the 
reasons they could not be changed) , the 
functional controls desired, and the best 
available machine layout at the time. As 
the machine and compartment designs pro- 
gressed, further meetings were held 
to clarify and combine ideas from both 
parties. A certain amount of redesign 
occurred on both sides at this stage. 

After a firm paper design was estab- 
lished, a mockup was the next step. 
Mockups are excellent for design reviews, 
but they can be expensive and difficult 
to transport. The mockup was substan- 
tially constructed to allow people to 
"try it on for size." Figures 2 through 
5 show how 50th and 95th percentile size 



male operators fit within the operator's 
area with the canopy in the low and high 
positions. The mockup was reworked in 
the process of design and proved to be an 
effective way to make good decisions on 
the prototype design features. 

Prototype construction was the next 
step taken on the LN 800. After final 
mockup acceptance and completion of de- 
tail drawings, two prototype machines 
were built (fig. 6). During the process 
of prototype construction, the consultant 
reviewed the prototype and commented on 
areas of improvement or difficulties not 
identified in the mockup stage. The pro- 
totype was then field-tested, and com- 
ments from the operators on the equipment 
were noted and evaluated as impartially 
as possible. The consultants reviewed 
the underground operation of the proto- 
type after the operators of the machine 
had a chance to familiarize themselves 



70 




FIGURE 2. - Cab mockup - 50th percentile operator with canopy in low position. 




FIGURE 3. - Cab mockup - 95th percentile operator with canopy in low position. 



71 





FIGURE 4. - Cab mockup - 50th percentile 
operator with canopy in high position. 



FIGURE 5. - Cab mockup - 95th percentile 
operator with canopy in high position. 




FIGURE 6. - Prototype cab and canopy on LN 800 continuous miner. 



72 



with the new machine and its operation. 
These evaluations were followed by rework 
of the prototype as required. The final 
stage of the prototype design reflected 
a value analysis , considering the advan- 
tages of the human-engineered design ver- 
sus its cost. 

At this point the design was ready 
for production. The LN 800 compartment 



design process also affected other ma- 
chines in the product line. It was 
very difficult to measure productivity 
increases or safety improvements rela- 
tive to the new design of the LN 800 
operator's area; however, the qualita- 
tive results showed in positive com- 
ments from the owners and operators of 
the equipment. 



PROBLEM AREAS 



Potential pitfalls to the design ap- 
proach described here include human fac- 
tors data, which are most often taken 
from samples of the military and there- 
fore represent a younger sample than 
the general population; this sample is 
also in above-average physical condition. 
One must also consider additional width 
and motion restrictions due to cap lamps, 
self -rescuers , and other belt-mounted 
equipment. Hand and foot access must be 
designed for gloved hands and heavy 
boots, and simplicity in design is es- 
sential. It is particularly difficult 
to maintain simplicity in low machines 
and still provide good human factors 
over a wide range of operator shapes and 
sizes. 



Another area of difficulty is spare 
controls. Many human factor specialists 
recommend different-length handles and/ 
or different-shaped knobs to provide tac- 
tile sensation of machine operation. 
This requires the mine to stock more 
spare parts. Even if the parts are 
stocked, the wrong spare knob or handle 
can easily be installed by mine mechan- 
ics, creating the potential for serious 
errors. In addition, electrical enclo- 
sure designs must be finalized in the 
initial machine design stages owing to 
the time involved in X/P certification by 
MSHA. Finally, even in long-term pro- 
grams such as the LN 800, only a limited 
time is available for review, testing, 
and redesign. 



DESIGN FEATURES 



Figure 7 shows a closeup of the LN 800 
operator area. One of its advantages is 
the single control lever for the convey- 
or; it moves right or left to swing the 
conveyor tail section and moves up and 
down to lift or lower the conveyor. The 
separation of the tram controls from the 
hydraulic controls is designed to in- 
crease safety. There is a logical se- 
quence to the pushbutton station; start- 
ing at the trailing cable entry end of 
the station, the operator proceeds for- 
ward on the machine for the normal start- 
ing sequence. The start buttons are 



recessed to prevent accidental tripping. 
The stop buttons are covered with plates 
or paddles such that a slap of the hand 
stops the machine in an emergency. This 
effectively acts as a backup for the 
emergency stop and makes the stop mech- 
anism easier to locate. Finally, the 
entire seat assembly swings out to allow 
access to control panels, circuit break- 
ers , and the miner water system without 
major disassembly of the machine. The 
seat itself is vertically adjustable, has 
lateral and lumbar support , and includes 
a self -draining design. 



CURRENT LOW-COAL DESIGNS 



The operator compartment on the Lee- 
Norse 285 miner (fig. 8) has a floating 
cab that doubles as a stabilizer shoe to 
allow a wider, deeper operator's area 



than the previous design with a separate 
stab shoe. The Lee-Norse 245 miner has a 
similar floating cab. The seating posi- 
tion is more comfortable in the floating 



73 




FIGURE 7. - Closeup of LN 800 operator area. 




FIGURE 8. - Floating cab and canopy on low-coal continuous miner. 



74 



1 1 


1 m 


iP 




1 





I 



I 



FIGURE 9. - Redesigned controls for low»coal continuous miner. 



cab, and the visibility is improved. The 
floating cab can be mechanically locked 
in a position clear of the ground, and 
the canopy height can be adjusted inde- 
pendently in the front and the rear 
of the compartment. We are currently 



reviewing this design to move the con- 
trols closer to the operator so that they 
move with the cab, rather than being 
mounted on the fender and fixed relative 
to the cab position (fig. 9). 



75 



EVALUATION OF "MINIMUM" AND "LOWEST PRACTICAL" WORKING HEIGHTS 

FOR SAFE USE OF CANOPIES 



by William W, Aljoe 



ABSTRACT 



This paper outlines an analytical ap- 
proach to determining the "minimum work- 
ing heights" and "lowest practical work- 
ing heights" necessary to allow the safe 
use of canopies on underground coal min- 
ing equipment. Each element of the work- 
ing height (mine floor to nearest over- 
head obstruction) is discussed in some 
detail, emphasizing the variability of 
the numerical values assigned to each 



element. The effects of machine type, 
machine frame height, and mine conditions 
on the working heights attainable with 
canopies are reviewed. With state-of- 
the-art cab and canopy technology, these 
variables will frequently prevent the 
safe use of canopies in low coal seams 
without extensive modifications to exist- 
ing equipment. 



INTRODUCTION 



Roof falls have historically been one 
of the most frequent causes of fatalities 
in underground coal mines. Preventing 
injuries and deaths from such falls is a 
difficult technological challenge, but 
progress is being made through a variety 
of engineering advancements. For exam- 
ple, the life-saving potential of proper- 
ly designed and constructed cabs or cano- 
pies on self-propelled face equipment has 
been demonstrated in numerous instances 
when operators escaped serious injuries 
from roof falls, some so massive that the 
machine was buried. Unfortunately, a 
number of technical problems remain un- 
solved in the design of functional opera- 
tor compartments for mining equipment 
working in low coal seams. 

Three principal problems are associ- 
ated with the use of canopies on low-coal 
equipment: "roofing" of the canopy dur- 
ing travel over uneven floors, limited 
vision of the machine operator, and se- 
verely cramped operator compartments. 
Design changes to minimize any of these 
problems usually worsen the impact of at 
least one of the other two. If an opera- 
tor is uncomfortable or has restricted 
vision, he or she tends to operate the 

^Mining engineer, Pittsburgh Research 
Center, Bureau of Mines, Pittsburgh, PA. 



machine in an unsafe manner, such as 
leaning beyond the protection of his can- 
opy or machine frame. Because many ex- 
isting cabs and canopies were not de- 
signed to compensate for this, numerous 
injuries to miners have occurred from 
collisions with the ribs, roofs, or other 
objects in the mining section. 

At present, Federal regulations require 
protective operator compartments in sec- 
tions having a minimum mining height 
of 42 in. However, extensive review of 
field data indicated that this require- 
ment could have better addressed the 
uniqueness among mining sections and the 
seriousness of operational problems with 
existing canopies in working heights be- 
tween 42 and 54 in. In numerous cases, 
low working heights prohibited the con- 
sistent use of canopies despite sub- 
stantial efforts by coal companies to 
achieve compliance with canopy regula- 
tions through innovative cab and canopy 
design concepts. Often, these designs 
were unsuccessful because only complete 
machine redesign or machine replacement 
would have allowed safe, efficient opera- 
tion with a canopy. 

This paper describes the results of 
approximately 3 years of research, spon- 
sored principally by the Bureau of Mines, 



76 



to document the application of cabs 
and canopies in low-coal mines. Most 
of this research was performed by Bitu- 
minous Coal Research, Inc., Monroeville, 
PA, under Bureau contract. ^ This paper 
describes a procedure that can be used, 
if the machine, operator's compartment. 



and canopy have been designed specifical- 
ly for low coal, to define the "minimum" 
and "practical" working heights at which 
canopies could be used without roofing 
and without restricting operator comfort 
or vision. 



THE MINIMUM WORKING HEIGHT WITH A CANOPY - WHAT DOES IT MEAN? 



The working height of the underground 
mining section is probably the most cri- 
tical factor governing the successful use 
of canopies. First, it is very Important 
to note that the term "working height" 
used here is not the same as the "mining 
height" contained in MSHA canopy regula- 
tions. Mining height as defined by MSHA 
is the total extracted height, from the 
mine floor to the unfinished roof; the 
minimum working height of a mining sec- 
tion is defined as the distance from tine 
mine floor to the lowest ovevhead olo- 
stvuetion on the section, if the obstruc- 
tion is not the result of poor mining 
practices. In some cases this obstruc- 
tion can be the mine roof itself, but it 
is usually a roof support device, machine 
trailing cable, or ventilation tubing 
suspended from the roof. Thus, the mini- 
mum working height will always be less 
than or equal to the minimum mining 
height, and the mining height at any lo- 
cation is equal to the working height 



plus the height (thickness) of the over- 
head obstruction at that point. 

Two other clarifications must be made 
about the meaning of the "minimum working 
height." First, it must be assumed that 
the machine frame or objects on top of 
the machine will not interfere prohibi- 
tively with operator vision. Second, the 
mine floor must be fairly level, with no 
sharp undulations. Because these condi- 
tions exist only rarely in actual prac- 
tice, a "lowest practical working height" 
with a canopy, usually larger than the 
minimum working height, must also be de- 
fined. Later in this paper, procedures 
for quantifying the lowest practical 
working height are given; these take into 
account the actual machine frame height 
and degree of mine floor undulation. 
However, let us first examine how the 
minimum working height under ideal condi- 
tions can be determined. 



PRODECURES FOR QUANTIFYING THE MINIMUM WORKING HEIGHT 



The first step toward quantifying the 
minimum working height with a canopy 
would be to divide the available vertical 
clearance into seven segments as shown in 
figure 1. The segments are defined as 
follows: (i) mine floor to bottom of cab 
deck, (2) thickness of deck and opera- 
tor's seat, (3) top of seat to opera- 
tor's eye level, (4) eye level to top of 
miner's cap, (5) cap to underside of can- 
opy» (^) canopy thickness, and i?) clear- 
ance between canopy and lowest overhead 
obstruction, 

^Bituminous Coal Research, Inc. "Ad- 
vancement of Cab and Canopy Design and 
Use in Coal Mines," Ongoing BuMines con- 
tract No. J0199055. 



Using available anthropometric data and 
state-of-the-art technology for mining 
machines, operator's compartments, and 
canopies, a minimum value can be assigned 
to each of these segments. Their sum is 
equal to the minimum working height with 
the canopy. However, the operator's 
size, machine type, machine model, and 
operator compartment design all have very 
important effects on the values assigned 
to each segment. In fact, completely new 
or radically different equipment technol- 
ogy could reduce these values substan- 
tially. It may be helpful, therefore, to 
consider how the minimum working height 
could be calculated for an existing ma- 
chine - a continuous miner with a very 
low frame. 



77 



7~-^ 




Extra header 
( 2 in thick) 



Bump 
(2 in high) 



V7Z7777. 



FIGURE 1. - Breakdown of minimum working height with canopies. 



Figure 1 was drawn to simulate a con- 
tinuous miner operator within the com- 
partment (sketch not to scale) ; let us 
start at the ground and work upward. Be- 
cause nearly all models of low-profile 
continuous miners can be equipped with 
"floating" cabs which slide along the 
mine floor in nonundulating conditions, 
the minimum value of segment 1 of figure 
1 would be zero. 

Segment 2 of figure 1 consists of two 
elements — the cab deck and the opera- 
tor's seat. The floating deck must be 
strong enough to withstand abrasion from 
the mine floor. If high-strength, heat- 
treated steel is used, the deck can 
be as thin as 1/2 in. However, mild 
steel is a much more common and inexpen- 
sive deck material; for practical pur- 
poses, a minimum deck thickness of 1 in 
(mild steel) is assumed here. 

The thickness of a seat or pad, when 
compressed by the weight of the operator, 
can also be as small as 1/2 in. In many 
cases, however, a higher seat is needed. 
For example, mud and water often spill 
into floating decks; if the seat were 
only 1/2 in above the cab deck, the oper- 
ator would have to spend most of his or 
her time cleaning out the compartment. 
Even on a slow-moving machine like a 
continuous miner, a thicker seat pad is 



often needed to cushion the operator when 
tramming over rough mine floors. The 
minimum seat thickness assumed in this 
example is 2 in. 

A realistic minimum value of segment 2 
in figure 1 would thus be 3 in — 1 in for 
the deck, and 2 in for the seat pad. 
Theoretically, this value could be lower 
(approximately 1 in); however, as subse- 
quent discussion will show, this reduced 
deck and seat thickness will not usually 
result in a substantial reduction of the 
minimum working height with a canopy. 

Segment Z is perhaps the most critical 
and controversial component of the mini- 
mum working height. The distance from 
the operator's seat to his or her eyes is 
governed by the operator's size and the 
internal configuration of the operator 
compartment. According to anthropometric 
data supplied by SAE,^ the seat-to-eye 
height would be approximately 23 in for 
both small (5th percentile female) and 
large (95th percentile male) machine op- 
erators if the operator can recline with- 
in the compartment. However, when a 
"sit-up" position must be utilized to run 

^Society of Automative Engineers. "De- 
velopment of SAE Guidelines for Under- 
ground Operator Compartments." Ongoing 
BuMines contract No. H0308110. 



78 



the machine effectively, the required 
seat-to-eye height can be as much as 29 
to 33 in for small and large operators, 
respectively. Obviously, the minimum 
working height with a canopy must also 
increase. To maximize the use of cano- 
pies in low coal, the operator's compart- 
ment must be designed to minimize the 
required seat-to-eye height. 

Most continuous miners in use today do 
not have compartments that allow the op- 
erator to recline (seat-to-eye height 23 
in). However, some presently available 
models do contain reclining seats , and 
compartments that provide at least a 
semireclining operator position can be 
retrofitted to other models. For the 
purpose of defining the minimim working 
height attainable with canopies on con- 
tinuous miners, it will be assumed that 
segment 3 of figure 1 can be reduced to 
23 in. 

The distance from the operator's eyes 
to the top of his or her cap, segment 4 
of figure 1, is approximately 6.5 in for 
both small and large operators. This 
value agrees with SAE anthropometric data 
and a survey of high-coal cab and canopy 
design done by Bendix.^ 

Segment 5 of figure 1 represents the 
"bounce space" required between the top 
of the operator's cap and the underside 
of the canopy. Based on numerous obser- 
vations of continuous miners in opera- 
tion, a value of 1.5 in was chosen; this 
was also the value selected by Bendix in 
the study mentioned above. 

Canopy thickness, segment 6 in figure 
1, is governed by its design and the 
strength of the material used. Solid- 
plate canopies are thinner than canopies 
made of structural steel tubing; if high- 
strength steel plate is used, it can be 

"^Farrar, R., R. Champney, and L. Wein- 
er. Survey on Protective Canopy Design, 
(contract H0242020, Bendix Corp.). Bu- 
Mines OFR 50-76, 1976, 163 pp.; NTIS PB 
251-67 2/AS. 



as thin as 1/2 in. As with cab decks, 
however, mild steel plate is much more 
common and inexpensive, so a minimum can- 
opy thickness of 1 in (mild steel plate) 
is assumed here. Although canopy thick- 
ness does not usually have a substantial 
effect on the minimum working height with 
the canopy, the overall design of the 
canopy top can be very important. 

Because the minimum working height with 
a canopy must be chosen so that canopy 
roofing does not occur, segment 7 of fig- 
ure 1 must be defined very clearly. This 
segment represents the minimum vertical 
clearance required between the canopy top 
and the nearest overhead obstruction nor- 
mally present in a flat coal mining sec- 
tion. Although this value is essentially 
arbitrary, it was chosen to be 4 in on 
the basis of observations of continuous 
miners in level seam conditions. This 
clearance is needed partly to overcome 
obstructions on the mine floor and part- 
ly to account for unexpected overhead 
obstructions. 

Even in flat , nonundulating coal mines 
where good housekeeping practices are 
followed, debris or an obstacle of some 
type will usually be present on the floor 
of the mining section. When the continu- 
ous miner trams over an obstacle, such as 
a pile of loose coal or a large rock, the 
machine and canopy will rise temporarily. 
If this occurs at the same spot in the 
mining section where an object protrudes 
below the level normally occupied by the 
lowest obstruction (e.g., a header board 
or trailing cable hanging beneath the 
bottom of required roof bolts), the local 
vertical clearance could be substantially 
less than the working height (mine floor 
to roof bolt) normally present on the 
section. To prevent the canopy from 
roofing, the maximum height of the canopy 
above the mine floor should be at least 4 
in less than the working height normally 
present. 

Adding the values assigned to segments 
1 through 7 of figure 1 yields the mini- 
mum working height needed to allow the 



79 



safe use of canopies on continuous 
miners: 

Segment in 

1 — ^Mine floor to cab deck 0.0 

2 — Deck and seat thickness 3.0 , 

S — Seat-to-eye height 23.0 



4 — Eye-to-cap height 6.5 

5 — Cap-to-canopy height 

("bounce space") 1.5 

6 — Canopy thickness 1.0 

7 — Clearance above canopy 4.0 

Total 39.0 



EFFECT OF MACHINE TYPE AND MINE FLOOR CONDITIONS 



Remember that the preceding example 
dealt with an ideal canopy installation — 
a slow-moving, low-profile machine with a 
properly designed operator compartment in 
a flat, dry, well-kept mining section. 
However, table 1 shows that the "minimum" 
working height needed to allow the safe 
use of canopies is different for differ- 
ent machine types. Also, "imperfect" 
conditions will increase the minimum 
working height with the canopy, and the 



effects of machine type and mining condi- 
tions can be quantified by reviewing the 
seven segments of figure 1. 

SEGMENT 1 - MINE FLOOR TO CAB DECK 

In the previous example, special care 
was taken not to use the term "ground 
clearance" when referring to this dis- 
tance. The ground clearance of a float- 
ing cab deck is zero, while the ground 



TABLE 1 . - Breakdown of minimum working heights with canopies , inches 





Machine type 


Segments of working 
height (fig. 1) 


Contin- 
uous 
miners 


Shut- 
tle 
cars 


Scoops 
and 
tractors 


Roof 
bolters , 
single- 
head' 


Roof 
bolters, 
dual- 
head' 


Cutters 
and 
face 
drills 


Loading 
machines 


1 — Mine floor to cab deck. 
2 — Deck and seat thickness 

2 — Seat-to-eye height 

4 — Eye-to-cap height 

5 — Cap-to-canopy height... 

6 — Canopy thickness 

7 — Clearance above canopy. 


20.0 

3.0 

^23.0 

6.5 

71.5 
1.0 
4.0 


20.0 

3.0 

^23.0 

6.5 

83.0 
1.0 
4.0 


^6.0 

3.0 

514.0 

6.5 

83.0 
1.0 
4.0 


20.0 

3.0 

423.0 

6.5 

71.5 
1.0 
4.0 


20.0 

3.0 

^23.0 

6.5 

71.5 
1.0 
4.0 


20.0 

3.0 

629.0 

6.5 

71.5 
1.0 
4.0 


20.0 
3.0 
629.0 
6.5 
71.5 
1.0 
4.0 


Minimum working height 
(sum of elements 1 
through 7) 


39.0 


40.5 


37.5 


39.0 


39.0 


45.0 


45.0 



'"Tram-only" or "drill-and-tram" compartment. 

2Floating compartment; if unworkable or unavailable, use ground clearance of opera- 
tor's compartment. 

■^Floating compartment not available; use ground clearance of operator's compartment 
(6 in normal) . 

^Reclining operator position; add 6 to 10 in for sit-up position. 

^Lie-down operator position; add 9 in for reclining, 15 to 19 in for sit-up 
position. 

6 Sit-up operator position; small operator. 

7 Slow-moving machines - tram speed 50 to 200 ft/min. 

8Fast-moving machines - tram speed 350 to 450 ft/min. 



80 



clearance of the frame of the continuous 
miner is commonly 6 in or more to prevent 
it from becoming hung up in the mine 
bottom. In broken, irregular, or muddy 
bottom conditions , hangup problems often 
become so severe that the deck must^be 
suspended above the mine floor at all 
times. The value of segment 1 of figure 
1 would not be zero if adverse bottom 
conditions prevail; it could be as large 
as the ground clearance of the machine 
f rame . 

Although floating operator compartments 
are available for several models of shut- 
tle cars, they must travel faster, far- 
ther, and more often than continuous 
miners, and they are much more suscepti- 
ble to hangup problems. As a result, the 
coal industry has not used floating com- 
partments on shuttle cars nearly as often 
as on continuous miners. When calculat- 
ing the minimum working height with a 
canopy on a shuttle car, the value of 
segment 1 of figure 1 will often be equal 
to the ground clearance of its main 
frame. However, this distance can be as 
low as zero if very good mine floor con- 
ditions exist. 

Although conceptual designs of floating 
cab decks have been developed for conven- 
tional equipment — cutters, face drills, 
and loaders — equipment manufacturers do 
not usually offer them as either "stan- 
dard" or "optional" items on new low- 
profile machines. Substantial modifica- 
tions or complete machine redesign would 
be needed to incorporate floating decks 
on most existing models of conventional 
equipment. Conceptual designs of float- 
ing cab decks have not been developed for 
scoops, tractors, and ramcars; substan- 
tial machine redesign would be needed. 



therefore, be the ground clearance of the 
machine, although new machine technology 
could lead to the development of mine- 
worthy floating compartments. 

Assigning a minimum mine-floor-to-cab- 
deck distance to roof bolters is espe- 
cially difficult because there is really 
no such thing as a "typical" roof bolting 
machine. Single-head and dual-head bolt- 
ers must be treated differently; some 
models require the operator to walk 
alongside the bolter when tramming, while 
others have tram compartments similar to 
those on the machine types previously 
mentioned. Also, for the purpose of spe- 
cifying a minimum working height with a 
canopy, only the tram function of the 
roof bolter can be considered. Because 
the operator must often drill and bolt 
while sitting or kneeling directly on the 
mine floor, the operator position shown 
in figure 1 would not apply to the tasks 
of drilling and bolting. 

Floating tram compartments are present- 
ly available for some models of single- 
head bolters whose drilling, bolting, and 
tramming functions are performed from the 
same compartment at the front of the ma- 
chine, near the drill head. For these 
machines the minimum mine-floor-to-cab- 
deck distance would be zero. Some mod- 
els of dual-head roof bolters also have 
floating compartments. However, many 
models of single-head bolters and almost 
all models of dual-head bolters have sep- 
arate tram compartments, whose ground 
clearance is usually equal to the ground 
clearance of the machine. For these ma- 
chines, the ground clearance of the frame 
of the roof bolter would often be a rea- 
sonable estimate of the value of segment 
1 of figure 1. 



Consequently, the mine-floor-to-cab- 
deck distance will not usually be zero 
for scoops, tractors, and ramcars. The 
ground clearance of the fixed deck need 
not be as large as the ground clearance 
of the machine frame, but many manufac- 
turers will make these two clearances 
equal. A reasonable estimate of the 
value of segment 1 of figure 1 would. 



In summary, the minimum distance re- 
quired between the mine floor and the 
bottom of the tram deck can range from 
zero to the ground clearance of the ma- 
chine frame, depending on machine type, 
model, and mine floor conditions. Each 
individual mine-machine combination must 
be examined carefully to determine how 
large this distance must be. 



81 



SEaiENT 2 - DECK AND SEAT THICKNESS 

As explained in the previous example 
of the continuous miner, machine design 
and mine floor conditions can affect 
the minimum thickness of the deck, and 
seat. However, the 3-in combined thick- 
ness assumed in that example represents 
a reasonable tradeoff between the best 
and worst deck material, floor condi- 
tions, and riding comfort. For practical 
purposes , a nominal 3-in deck and seat 
thickness can be used when calculating 
the minimum working height with a canopy, 

SEGMENT S - SEAT-TO-EYE-HEIGHT 

The variable nature of this distance on 
a continuous miner was discussed in the 
previous example. Theoretically, the 23- 
in seat-to-eye height also represents the 
minimum height attainable on other types 
of electric face equipment. However, 
compartments on most existing low-profile 
machines were designed for sit-up opera- 
tion; these must be modified to provide 
the minimum possible (23-in) seat-to-eye 
height. In many cases such modifications 
would be difficult or unfeasible because 
of original machine design, and the mini- 
mum seat-to-eye height would be 29 in, 
even for the smallest operators. Almost 
all cutters, face drills, and loaders 
presently require operators to sit up- 
right at all times. 



types , the long axis of the operator' s 
body is parallel to the travel direction, 
and the attempt to look forward from the 
lie-down position would result in exces- 
sive head and neck strain. Changing 
seats or turning around to face the oppo- 
site tram direction would also be ex- 
tremely difficult. Therefore, the lie- 
down operator position and 14-in seat- 
to-eye height are applicable only to 
scoops and tractors with transverse 
compartments. 

Unfortunately, only a few models of 
scoops and tractors have been designed to 
accommodate operators in the lie-down po- 
sition. Substantial modifications would 
be needed on most models to provide ade- 
quate leg room while allowing the opera- 
tor to remain protected by the compart- 
ment. Even if such modifications are 
made, the resulting compartment configur- 
ation could place the operator's eyes far 
below the top of the machine frame, pro- 
hibiting vision to the opposite side of 
the entry, 

SEGMENT 4 - EYE-TO-CAP HEIGHT 

No significant type-to-type or model- 
to-model variations exist for this dis- 
tance; a minimum value of 6.5 in can be 
used in all cases. 

SEGMENT 5 - CAP-TO-CANOPY "BOUNCE SPACE" 



Some models of scoops and tractors , 
however, can be modified to allow machine 
operation from a "lie-down" position. 
SAE anthropometric data^ indicate the 
minimum operator seat-to-eye height in 
the lie-down position would be approxi- 
mately 14 in for both small and large 
persons. In the transverse or "side- 
saddle" compartments characteristic of 
scoops and tractors, the long axis of the 
operator's body (head to toe) is perpen- 
dicular to the direction of machine trav- 
el, and the operator needs only to rotate 
his or her head to see alongside the ma- 
chine in the forward and reverse direc- 
tions. On almost all other machine 

^Work cited in footnote 3. 



When traveling over mine floors of 
equal roughness, the operators of fast- 
moving machines — shuttle cars, scoops, 
and tractors — will need approximately 
twice as much "bounce space" as opera- 
tors of slow-moving machines — continuous 
miners, cutters, face drills, loaders, 
and roof bolters. Therefore, the values 
assigned to segment 5 of figure 1 would 
be 3,0 and 1.5 in, respectively. 

SEGMENT 6 - CANOPY THICKNESS 

The same statements made about deck 
thickness apply to canopy thickness; most 
existing low-coal canopies are made of 
1-in-thick mild steel rather than 1/2-in- 
thick high-strength steel. For practical 



82 



purposes, 1 in should be allowed for can- 
opy thickness when calculating the mini- 
mum working height with a canopy on ex- 
isting equipment. 

SEGMENT 7 - CLEARANCE ABOVE CANOPY 

The value of this dimension on con- 
tinuous miners — 4 in — applies equally to 
all machine types and models as long as 
large-scale mine floor undulations are 
not present. As will be shown later in 
this paper, machine type and model do 
have significant effects on the clearance 
required above the canopy when mine floor 
undulations occur. 

SUMMARY 



if mineworthy 
developed. 



floating decks can be 



2. The deck and seat thickness of 3 
in can be reduced to about 1 in if high- 
strength steel and minimal seat padding 
are used. Conversely, some machine oper- 
ators may insist upon higher seats if mud 
and water spillage are excessive, and 
more seat padding or suspension may be 
needed to cushion the operator against 
rough rides. 

3. The required seat-to-eye height is 
governed by the control configuration and 
interior dimensions of the operator's 
compartment. Substantial type-to-type 
and model-to-model variations exist. 



Table 1 summarizes the values to be as- 
signed to segments 1 through 7 of figure 
1 when calculating the minimum working 
heights attainable with canopies on ex- 
isting equipment. As noted in table 1, 
many of these values can be either higher 
or lower because — 

1. Floating cab decks may or may not 
be available or feasible on existing 
machines. If a floating deck is not 
commercially available for a particular 
equipment type, a nominal compartment 
ground clearance of 6 in is listed in ta- 
ble 1. However, the actual ground clear- 
ance of the fixed deck can be lower than 
6 in, and it could be reduced to zero 



4. "Bounce space" between the opera- 
tor's cap and the canopy depends on ma- 
chine tram speed. 

5. Canopy thickness can be reduced if 
stronger steel is used; however, if steel 
tubing is used for the canopy, its thick- 
ness will be greater than 1 in. 

6. Required clearance above the canopy 
in a flat coal seam depends on the number 
and height of unexpected obstructions on 
the mine roof and floor; these will vary 
greatly from mine to mine, from section 
to section in a mine, and within the same 
mining section. 



LOWEST PRACTICAL WORKING HEIGHTS WITH CANOPIES 



The ideal conditions needed to achieve 
the minimum working heights with canopies 
listed in table 1 — flat, nonundulating 
seams and equipment that does not ob- 
struct operator vision — will not be pres- 
ent on most mining sections in operation 
today. Therefore, we should define the 
"lowest practical working height" with 
canopies, again using state-of-the-art 
technology, to take into account the ad- 
verse effects of mine floor undulations 
and visual obstructions caused by the 
canopy and machine frame. 



EFFECTS OF MACHINE FRAME HEIGHT 

The machine frame almost always ob- 
structs vision in low coal. Operators 
frequently lean outward to see alongside 
their machines because this is the only 
vision available when clearance between 
the frame and the mine roof is limited, 
even when a canopy is not present. The 
canopy introduces yet another visual ob- 
struction, one that many machine opera- 
tors consider "unnecessary" and "danger- 
ous." The following paragraphs describe 



83 



a simple procedure for calculating the 
lowest practical working height with a 
canopy from the machine frame height. 

When defining a relationship between 
the machine frame height and the lowest 
practical working height at which a can- 
opy can be used, one critical factor must 
be specified — the vertical distance be- 
tween the top of the machine frame and 
the operator's eye level. A wide range 
of opinions was received regarding the 
distance needed to assure "adequate" op- 
erator vision. For example, in the Ben- 
dix canopy survey^ equipment manufactur- 
ers recommended that the operator's eyes 
be placed 3 to 8 in above the machine 
frame. Conversely, the fact that low- 
coal equipment operators can often run 
their machines using solely "down-the- 
side" vision has been used as evidence 
that their eyes can be at any level below 
the top of the main frame. Considerable 
disagreement will continue to exist no 
matter what frame-to-eye level distance 
is chosen; however, for simplicity, it 
is assumed here that the operator's eyes 
must be at the same level as the top of 
the machine frame to assure adequate vi- 
sion. Using this assumption and the pro- 
cedures described earlier in this ar- 
ticle, the "lowest practical working 
height" with canopies can be determined 
directly from the machine frame height. 

Referring again to figure and table 1, 
segments 1 through 3 define the minimum 
distance between the mine floor and the 
operator's eye level. Since it is as- 
sumed the machine frame will not obstruct 
operator vision if it is below eye level, 
the lowest practical working height with 
a canopy will not be governed by the ma- 
chine frame height if it is less than the 
sum of segments 1 through S, For such 
low-frame machines, the lowest practical 
working height in a flat coal seam will 
be equal to the minimum working height 
listed in table 1; operator headroom 
rather than vision will be the limiting 
factor. 

^ork cited in footnote 4. 



The first four columns of table 2 show 
how the machine type, compartment ground 
clearance, and operator seating position 
combine to determine the minimum machine 
frame height to be considered in the 
analysis of the lowest practical working 
height with a canopy. For example, if 
the operator compartment on a continuous 
miner forces a 95th percentile size male 
to assume an upright position (33 in from 
seat to eyes), the minimum frame height 
to be considered will be 36 in (33 in + 3 
in deck and seat thickness) despite the 
compartment's ability to float on the 
mine floor. On the other hand, scoops 
and tractors with frames as low as 23 in 
can be considered because the operator's 
ability to lie down (if modifications to 
the compartment are made) places his or 
her eyes at this height despite the nomi- 
nal 6-in compartment ground clearance. 
If the actual machine frame height is 
greater than the minimum applicable 
height given by table 2, it is assumed 
that segment 1,2, or 3 of table 1 would 
be increased to place the operator's eyes 
at the same level as the frame. 

The fifth column of table 2 shows 
how the lowest practical working height 
with a canopy in a flat coal seam is 
calculated from the machine frame 
height. The sum of segments 4 through 7 
in figure 1 and table 1 is the required 
vertical clearance between the machine 
frame (eye level) and the nearest over- 
head obstruction. This clearance is 14.5 
in for fast-moving machines and 13.0 
in for slow-moving machines because the 
need for operator headroom increases 
with tram speed. Thus, in level seams, 
one of the two formulas listed in the 
fifth column of table 2 can be used to 
calculate the lowest practical working 
height. 

Note that if the lowest practical work- 
ing height were calculated with the re- 
quirement that the operator's eyes be 
placed at a certain level above the top 
of the machine frame, for example, 3 in, 
the result would be the same as if the 
formulas listed in table 2 were used. 



84 



TABLE 2. - Formulas for calculating "lowest practical work heights" 
with canopies in flat coal seams 





Compart- 




Minimum appl- 


Formula for 




ment 




cable frame 


lowest prac- 


Machine type 


ground 


Operator seating 


height , 


tical work- 




clear- 


position^ and size 


ground 


ing height, 




ance, 




clearance 


frame height 




in 




plus — 


plus — 


Continuous miners... 


0-6 


Reclining - 5th pet female 

and 95th pet male. 
Sitting - 5th pet female 
Sitting -95th pet male.. 


26 in 

32 in 
36 in 


13 in 


Shuttle cars 


0-6 


Reclining - 5th pet female 

and 95th pet male. 
Sitting - 5th pet female 
Sitting -95th pet male.. 


26 in 

32 in 
36 in 


14.5 in 


Roof bolters,^ cut- 


0-6 


Reclining - 5th pet female 


26 in 


13 in 


ters, face drills, 




and 95th pet male. 






and loading 




Sitting - 5th pet female 


32 in 


' 


machines . 




Sitting -95th pet male.. 


36 in 




Scoops and tractors. 


63 


Lying - 5th pet female 

and 95th pet male. 
Reclining - 5th pet female 

and 95th pet male. 
Sitting - 5th pet female 
Sitting -95th pet male.. 


17 in 

26 in 

32 in 
36 in 


14.5 in 



'Modifications to 
lying-down positions. 

^Tram canopy only. 

^Floating operator 
or less than 6 in. 



operator compartments may be necessary to allow reclining and 
"Pet" indicates percentile in entries in this column. 

compartments unavailable; actual ground clearance may be more 



Although the minimum applicable frame 
height would be 3 in lower than listed in 
table 2, the numerical value added to the 
frame height to obtain the lowest practi- 
cal working height would be 3 in greater 
(16.0 in or 17.5 in versus 13.0 in or 
14.5 in). On the other hand, if the op- 
erator's eyes are allowed to remain below 
the level of the machine frame, the low- 
est practical working height with a can- 
opy would be equal to the minimum working 
height listed in table 1. The minimum 
applicable frame height in this ease 
would be equal to the minimum working 
height minus 4 in to allow for rough bot- 
tom conditions which may cause the frame 
itself to hit the roof. 



EFFECTS OF MINE FLOOR UNDULATIONS 

Until this point , it was assumed that 
mine floor undulations (abrupt changes in 
eoalbed elevation) were not prevalent. 
However, all mine floors undulate to some 
degree, and both the miaehine frame and 
the canopy will experience some amount of 
upward or downward movement , or excur- 
sion, when tramming through the undula- 
tion. The amount of canopy excursion 
must be added to either the minimum work- 
ing height (table 1) or the lowest prac- 
tical working height in a flat coal seam 
(table 2) to obtain the lowest practical 
working height with a canopy in undulat- 
ing conditions. 



85 



Overall canopy excursion can be cal- 
culated geometrically and depends on 
three major factors: (1) the location 
of the operator's compartment and can- 
opy on the machine, (2) the degree of 
change in the slope of the coalbed floor 
(degree of undulation) , and (3) the de- 
sign of the cab and canopy. Floating 
operator compartments can reduce canopy 
excursion somewhat but cannot always 
eliminate it. Figures 2 through 7 illus- 
trate canopy excursion and show how it 
can be calculated. 



Canopy Excursion on 
End-Driven Equipment 

Figures 2 and 3 are scale drawings of a 
typical continuous miner tramming over a 
"severe" undulation — an abrupt 6° change 
in the slope of the mine floor. When the 
miner is in the position shown in figure 
2, the maximum amount of vertical canopy 
excursion is taking place because its 
center of gravity (pivot point) has just 
crossed the undulation point. The maxi- 
mum possible excursion E is equal to D 



Distance from machine pivot 
point to canopy, D 





'^m\wiim^im^jj^m\^ii^\^^m^mm\mm 



Undulation 
point 



Angle of 

mine floor 

undulation, 0- 



"Upward canopy excursion; E 

FIGURE 2. - Upward canopy excursion on end-driven equipment. 




Maximum downward 
canopy excursion = 9' 



Cab -canopy hinge 
point 



Machine pivot point 
and undulation point 



FIGURE 3. - Canopy excursion reduction with floating operator compartment. 



86 



(sin 0), where D is the distance from the 
machine's center of gravity to the point 
on the canopy being considered, in this 
case the rear edge, and is the degree 
of mine floor undulation. In figure 2, D 
equals 140 in and is 6° , so E equals 
14.6 in. 

If the operator's compartment and can- 
opy cannot float downward below the orig- 
inal level of the crawlers of the miner, 
as in figure 2, the lowest practical 
working height with a canopy would be 
14.6 in greater than indicated in table 1 
or 2, and the rear end of the canopy 
would "roof out" first. However, as 
shown in figure 3, floating operator com- 
partments on continuous miners are usual- 
ly hinged at the end closest to the cut- 
ting heads, with the rear end free to 
float downward until stopped mechanical- 
ly, in this case by the rear bumper of 
the miner. The amount of downward canopy 
movement depends on (1) the location of 
the front and rear ends of the canopy 
with respect to the hinge point and 
(2) the distance below the crawler at 
which the deck is downstopped. To show 
how this downward movement can be calcu- 
lated, let us examine figure 3. 

Figure 3 shows the full-down position 
of the operator's compartment — note that 
the deck is not resting on the mine 
floor. The distance between the downstop 
block and the rear bumper of the miner 
when the deck is in the level position 
(fig. 2) represents the maximum downward 
excursion of the rear end of the canopy, 
in this case 9 in. Subtracting this val- 
ue from the 14.6 in of initial upward 
canopy excursion yields an overall upward 
excursion of 5.6 in at the rear end of 
the canopy. 

Now the excursion of the front end of 
the canopy must be examined. The angle 
through which the canopy rotates when it 
floats downward is the same at both its 
front and rear ends, and the amount of 
downward movement at the front end de- 
pends on its horizontal distance from the 
hinge. From geometry, the downward ex- 
cursion was found to be 2.1 in, using 
compartment dimensions provided by the 



manufacturer. Subtracting this downward 
movement from the 10-in upward excursion 
of the front end [from the formula E 
= (D) (sin 0) at D = 96 in] yields a to- 
tal canopy excursion of 7.9 in. Thus, if 
the front and rear ends of the canopy 
were at the same level before the 6° 
undulation was encountered, the front 
end would strike the roof or roof sup- 
ports first (7.9 in versus 5.6 in overall 
excursion) . 

Note in table 1 that the minimum work- 
ing height for canopy-equipped continuous 
miners in level conditions was found to 
be 39.0 in. The lowest practical working 
height with the canopy on the miner in 
figures 2 and 3 can now be calculated: 



in 



Minimum working height in level 
conditions (table 1) 39.0 

Maximum upward canopy excursion 
(fig. 3) 7.9 

Total 46.9 

Although figures 2 and 3 show a 
crawler-driven continuous miner, the pro- 
cedure used to calculate canopy excursion 
would be the same for any wheel-driven 
machine whose operator's compartment is 
at the front or rear end. Several models 
of shuttle cars, roof bolters, scoops, 
and tractors fall into this category. 
Because the maximum canopy excursion will 
take place when the axle closest to the 
operator's compartment crosses the undu- 
lation point, the distance D depicted in 
figures 2 and 3 would be the distance 
from the end of the canopy to the axle of 
the nearest wheel. Also, if the opera- 
tor's compartment can float downward at 
both ends, instead of being hinged, the 
amount of downward movement would be the 
same at both ends of the operator's com- 
partment, and the end of the canopy far- 
thest from the axle would roof out first. 

In general, the procedure for determin- 
ing the lowest practical working height 
with canopies on end-driven equipment can 
be summarized as follows: 



87 



1. Find the potential upward excur- 
sion from the formula E = (D) (sin 0) for 
the actual slope change angle and pivot- 
point-to-canopy distance, 

2. Use actual compartment geometry to 
calculate the maximum excursion reduction 
possible, as in figure 3. 

3. Add the difference of items 1 
and 2 to the height obtained from ta- 
ble 1 or table 2 for the machine under 
consideration. 

The resultant distance is the working 
height that must be provided to keep the 
canopy from roofing when undulating mine 
floor conditions prevail. The same pro- 
cedure can be used to calculate the 
"lowest practical working height" with 
the machine itself , simply by adding the 
maximum upward excursion of the machine 
frame (usually near its rear end) to the 
original machine frame height. 

Canopy Excursion on 
Center-Driven Equipment 

Figures 4 through 7 illustrate canopy 
excursion as it would occur on a shut- 
tle car whose operator's compartment is 
located between the tramming wheels. 
Most low-profile shuttle cars fall into 
this category, along with cutters, face 
drills, and many models of roof bolters. 

Canopy excursion on center-driven 
equipment is different from that on end- 
driven equipment in three important ways. 
First, the a&ntev portion of the canopy 
on a center-driven machine will experi- 
ence greater upward excursion than either 
the front or rear end. Second, the 
wheelbase of a center-driven vehicle is 
the critical dimension governing the 
overall canopy excursion. Finally, both 
upward and downward mine floor slope 
changes can cause upward canopy excur- 
sion on center-driven machines. There- 
fore, four individual mine-machine-canopy 
configurations are shown in figures 4 
through 7 to describe all situations 
where canopy roofing can occur. 



Figure 4 shows a center-driven shuttle 
car whose deck is fixed at 6 in above the 
mine floor, tramming over an upward undu- 
lation. This situation represents the 
maximum upward excursion possible with a 
center-mounted canopy and illustrates 
most clearly the geometrical relationship 
between the cab, canopy, machine, and 
mine floor. Note first the enlarged 
sketch of the transition area around the 
point of coalbed slope change (undulation 
point). The maximum canopy excursion (E) 
occurs when the wheels of the shuttle car 
straddle the undulation point and the 
upward projection of the undulation point 
bisects the wheelbase. From geometry, it 
can be seen that E = (w/2) sin (0/2), 
where E is the upward canopy excursion, w 
is the wheelbase of the machine, and is 
the angle of mine floor undulation. 

Applying this formula to the shuttle 
car in figure 4 (w = 120 in, 0=6°) 
yields a canopy excursion of 3,14 in. 
Note also that the center portion of the 
canopy is closest to the mine roof, which 
has been drawn parallel to the mine floor 
in figure 4, 

The lowest practical working height 
with a canopy on this shuttle car can now 
be calculated (the minimum working height 
is 46,5 in because 6 in of compartment 
ground clearance is added to the sum of 
segments 2 through 7 of table 1): 

in 

Minimum working height 46, 5 

Overall canopy excursion 
(fig. 4) 3,1 

Total 49,6 

Figure 5 shows a slightly different 
shuttle car, this one with a floating 
compartment, as it trams over an upward 
mine floor undulation. The formula for 
calculating the potential upward canopy 
excursion is the same as in figure 4, 
E = (w/2) sin (0/2), However, the over- 
all canopy excursion would be equal to 



88 



-w=l20"- 



^^^^^^i^mmMimmm^mm 



"^^^^^mrmrm 




Direction 



^mum 



Transition 
area 



■Undulation 
point 



Closeup of transition area 
(exaggerated) 







E=3.I4 



FIGURE 4. - Upward canopy excursion on center-driven equipment (shuttle cor). 



-w = 96'- 



"^^^^^^^^^^^^^^^^^^^^^^^^^ 



Direction 




Upward excursion negated by 
tree-floating deck 



Undulation 
point 



0=6" 



FIGURE 5. - Center-driven shuttle cor with floating operator compartment - upward undulation. 



zero if the cab deck were allowed to 
float downward far enough to negate the 
upward movement. Then the lowest practi- 
cal working height with a canopy would be 
40.5 in, the same as in table 1, 

Figure 6 shows the same shuttle car as 
in figure 5, this time tramming across a 
downward mine floor undulation. However, 
instead of floating downward into open 
space, as in figure 5, the compartment 
in figure 6 will be pushed upward by the 
mine floor as the shuttle car crosses the 



undulation point. The maximum canopy ex- 
cursion occurs when the undulation point 
contacts the midpoint of the deck and is 
calculated from the formula E = (w/2) sin 
(G/2). 

Figure 7 shows a shuttle car whose 
operator's compartment is fixed at 6 
in above the mine floor, tramming across 
a downward mine floor undulation. The 
compartment ground clearance enables it 
to pass over the undulation point as 
though the floor were level. The canopy 



89 




No excursion reduction possible 



Undulation 
point 



of travel 



FIGURE 6. - Center-driven shuttle car with floating operator compartment - downward undulation. 




Ground clearance negates upward 
canopy excursion 



Undulation 
point 



of travel 



FIGURE 7. - Center-driven shuttle car with fixed operator compartment -> downward undulation. 



excursion in this situation would be neg- 
ligible, and the lowest practical working 
height with a canopy would be the same as 
the height found in table 1 or 2. 

Summar y 

Table 3 lists the range of canopy ex- 
cursions that can be expected when "se- 
vere" mine floor undulations of 6° are 
encountered. The values in the right- 
hand column of table 3 were obtained 
from the formulas (D) (sin 0) and (w/2) 
sin (0/2) , for end-driven and center- 
driven equipment, respectively. Obvi- 
ously, end-mounted canopies will almost 
always experience more excursion than 
center-mounted canopies because the undu- 
lation angle is halved in the latter 
calculation, 

A wide range of potential canopy ex- 
cursions exists for continuous miners 
for two reasons: (1) Different models 



TABLE 3, - Typical values of canopy 
excursion' 

Canopy 
Machine type excursion,^ 

in 
Continuous miners, all 

end-driven 6-15 

Shuttle cars, center-driven, 3- 4 
Shuttle cars, end-driven,,,, 6- 8 
Scoops and tractors, center- 
driven , 2- 3 

Scoops and tractors, end- 
driven 6- 8 

Roof bolters - single- and 

dual-head, center-driven,,, 2- 3 
Roof bolters - single- and 

dual-head, end-driven 6- 8 

Cutters, face drills, and 
loaders, all center-driv en, 2- 3 
' Severe mine floor undulations assumed; 
slope change = 6° , 

^Excursion determined by machine model, 
compartment location, and design of cab 
and canopy. 



90 



of continuous miners can have signifi- 
cantly different pivot-point-to-canopy 
distances, and (2) the design of the 
hinged, floating cab and canopy has an 
important effect on the amount of excur- 
sion reduction attainable. Cab and can- 
opy design is also very important when 
calculating canopy excursion on any end- 
driven machine. 

Excursions of center-mounted canopies 
do not vary greatly from machine to ma- 



chine because wheelbases do not vary as 
much as pivot-point-to-canopy distances. 
Also, figures 6 and 7 show that floating 
compartments experience move canopy ex- 
cursion than fixed compartments when 
downward mine floor undulations are en- 
countered. Therefore, the only advantage 
of using floating operator compartments 
on center-driven machines is that they 
eliminate the initial compartment ground 
clearance, segment 1 of figure 1 and 
table 1. 



COMPLIANCE WITH MSHA CANOPY REGULATIONS 



As stated earlier, present MSHA regula- 
tions require the use of canopies on all 
face equipment when the minimum mining 
height on the section is 42 in or great- 
er. However, even though the minimum 
working heights with canopies listed 
in table 1 are less than 42 in for some 
equipment types, there are several rea- 
sons why compliance may be difficult or 
impossible in low-coal situations: 

1. The thickness of required roof sup- 
ports or other roof-mounted obstruc- 
tions must be added to the minimum work- 
ing height to obtain the minimum mining 
height. In mines where planks, cross- 
bars, or rails are needed for extra roof 
support, the minimum mining height (mine 
floor to unfinished roof) needed to allow 
the safe use of a canopy will almost al- 
ways be greater than 42 in. 

2. Floating operator compartments are 
not presently available for all equipment 
types and models. Minimization of com- 
partment ground clearance is essential to 
the increased used of canopies in mining 
heights close to 42 in. 

3. The need for equipment operators to 
assume upright positions makes it physi- 
cally impossible for them to remain be- 
neath a canopy without discomfort when 
the mining height is limited to 42 in. 
This problem cannot be resolved until 
compartments are designed to allow pro- 
tected machine operation from a reclining 
or lying down position. 

4. Canopy excursion due to mine floor 
undulations can cause roofing to 



occur in mining heights much greater than 
42 in. 

5. The heights listed in tables 1 and 
2 were based mostly on static human body 
and equipment dimensions rather than 
dynamic work procedures. The effects 
of the machine frame, the canopy, and 
machine-mounted obstructions as the ma- 
chine is operated will be very different 
from machine to machine. Each operator's 
willingness to tolerate constraints to 
his comfort and vision will also be 
different. 

6. In many mines, the mining height 
fluctuates above and below 42 in very 
frequently. When the mining height is 
below 42 in, canopies are not required, 
so machine operators usually remove them 
to improve comfort and vision. \ However, 
these machines would be "out of compli- 
ance" when the mining height rises above 
42 in. Canopies are often very heavy, 
cumbersome, and time-consuming to install 
and remove, especially in the confined 
quarters of low coal seams. Therefore, 
both the mine operator and the workers on 
the mining section tend to be reluctant 
to reinstall canopies that have just been 
removed, if they know that in the near 
future the mining height will again fall 
below 42 in. 

In conclusion, it is obvious that low- 
coal canopy problems are very complex 
and can be resolved only if the exact 
machine, mine conditions, and equipment 
operator involved with the problem are 
defined. 



I 



SU.S. CPO: 1981-505-019/5083 



INT.-BU.OF MINES, PGH., PA. 27751 



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